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GIFT  OF 


A  consideration  of  various  factors  affecting 
the  net  duty  of  irrigation  water 


Philip  Rowland  Roosegaarde  Bisschop 

B .  S .  ( Uni v ersity  of  South' , jAtfr'i c a,)  £ 9 18 
In  *e««*da^«  *l^^:v^£^ 

THESIS 

Submitted  in  partial  satisfaction  of  the  requirements  for  the 

degree  of 

MASTER  OP  SCIENCE 
in 


Civil  Engineering 

in  the 
GRADUATE  DIVISION 

of  the 
UNIVERSITY  OP  CALIFORNIA 


Approved  _   .  ______ 

^/Tinstructor  in  Charge 


Deposited  in  the  University  Library 


Librarian 


81  ej?  ?frjK>JWl£. 

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»*  to. 


a  .a" 


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lo 


iti 


Letter  of  Transmittal 


Prof.  Charles  Derleth,  Jr., 

Dean  of  the  College  of  Civil  Engineering, 

University  of  California. 

Dear  Sir: 

In  accordance  with  the  regulations 
of  the  College  of  Civil  Engineering,  I  herewith 
beg  to  submit  to  you  for  your  approval  my  Thesis 
for  the  degree  of  Master  of  Science. 

I  remain,  Sir, 

Yours  faithfully, 


Berkeley, 

April  30th,  1921. 


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siii  ri'^iw  sortsfcicoos  «I 

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a  lo  is^BBM  lo 


f  *  1  a  1  a*t  wo  ¥ 


TABLE  OP  CONTENTS  p 


Letter  of  Transmittal. 


Chapter  I 

Introduction 

Definition  of  net  duty  and  max- 
imum economical  duty 


Chapter  II 

The  Texture  and  Structure  of  the  Soil . , 

Grades  of  soil 

Structure  of  the  soil 

The  moisture  contained  in  the  soil 


Chapter  III  28 

The  Climate  .........  ......................... 

The  annual  precipitation  and  its 

distribution  ........  .  ................. 

The  start  of  the  Irrigation  System  ....... 

Chapter  IV  34 

Moisture  Distribution  in  the  Soil  ............ 

Downward,  upward  and  lateral 

movement  of  soil  moisture  ............ 

The  extent  of  distribution  ............... 

Results  of  field  experiments  ............. 

Conclusions  reached  ...................... 

Chapter  V  5^ 

Character  of  Soil  and  Subsoil  ................ 

Hardpans  ................................. 

Gravel   and  sandy  subsoils  ................ 


Chapter  VI  67 

Ejrapj)ration,    Percolation  and  Surf  ace.  J/asJbe 
Losses    ...................................... 

The  process  of  evaporation  ............... 

Cultivated  and  uncultivated  soils  ..... 

Mulching  .............................. 

Furrow  irrigation  ..................... 

The  effect  of  the  type  of  soil  on  per- 
colation losses  ......................... 

Size  of  irrigation  head  .................. 

Frequency  of  application  .............. 

Length  of  run  ......................... 

Lateral  percolation  in  furrows  ........ 

Surface  waste  ..... 


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03 

....  a  : 


act  I   ,f>n-? 

.no 


.u  jaio/n  IIoa»  ic  tnsr.i.svo 
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sir.i'ioqxs  Mail  'to  a^ 

.  .  b  9ri  o  B  e^c   3  no  1  s  .0  1  one  U 


bed' av  Mi 


Page 

Chapter  VII  93 

The  Fertility  of  the  Soil 

Need  of  fertilizers 

The  function  of  organic  matter  in 

the  soil 

Cover  crops 

Chapter  VIII  99 

The  Crops 

Plant  growth 

The  effect  of  irrigation  at  different 
periods  of  plant  growth 

American  irrigation  practice  on  dif- 
ferent crops 

Diversification  of  crops 

Chapter  IX  ]_09 

Yields  of  Various  Crops  under :...VaryJLn£ 

Amounts  of  Irrigation  Applications 

Results  of  experiments  on 

( 1 )  Alfalfa 

(2)  Potatoes 

(5)  Cereals 

(4 )  Citrus  fruits 

(5)  Deciduous  fruits 

Chapter  X 
Tabled" 

(1)  The  net  and  gross  duty  of  various 

irrigation  projects  for  the  year 
1917 

(2)  Distribution  of  irrigation  water  for 

net  duty  on  various  projects  for 
the  years  1912-1919 

(3)  Average  seasonal  duty  of  water  on 

various  Irrigation  Projects  for 
the  years  1912-1917.... 


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.  .  .  , aqoto 

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SI 

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•taw  noli^'-I/nJ:  1o   nol 


BIBLIOGRAPHY 
(References  are  indicated  by  number.) 

1.  Soils — Lyon,  Pippin  and  Bucionan. 

2.  Principles  of  Irrigation  Practice—Widtsoe. 

3.  Irrigation  and  Drainage- -King . 

4.  Irrigation  Management- -Newell. 

5.  Irrigation  in  the  United  States--Teele. 

6.  Irrigation  Practice  and  Engineering,  Vol.I?-Etchevery. 

7.  Soils--Hilgard. 

8.  Physics  of  Agriculture --King. 

9.  Evaporation  from  Irrigated  Soils--Portier  and  Beckett 

--United  States  Department  of  Agriculture ,, Bulletin  248. 

10.  Distribution  of  water  in  the  soil  in  Furrow  Irrigation 

--Loughridge  and  Portier,  United  States  Department 
of  Agriculture,  Bulletin  203. 

11.  Irrigation  and  Soil  Moisture  Investigations  in 

Western  Oregon--W.  L.  Powers,  Oregon  Agricultural 
Experiment  Station,  Bulletin  122. 

12.  Duty  of  Water  investigations—Don  H.  Bark,  Ninth  Bi- 

ennial Report  of  the  State  Engineer  of  Idaho. 

13.  The  Duty  of  Water  in  Cache  Valley,  Utah—Harris,  Utah 

Agricultural  College  and  Experiment  Station, 
Bulletin  173. 

14.  The  Movement  of  Water  in  Irrigated  Soils — Widtsoe  and 

McLaughlin.  Utah  Agricultural  College,  Experiment 
Station,  Bulletin  115. 

15.  Yields  of  Crops  with  Different  Quantities  of  Irriga- 

tion Water--Widtsoe  and  Kerrill,  Utah  Agricultural 
College  Experiment  ^tateion,  Bulletin  117. 


Em-  nlqq  Jt'3.  ,  no  -&I  -  -a  I  ioS  •  I 
oJt:*Ai8l--xiI  lo  aalqloalil  -2 
ifiB  no  i  4s  si-  IT:  I  -S 


-3 

-8 


rrt    * 


I     -.01 


9LjS5"i.     »  JJtTJ-' J.//0  L'l  V 

•axe      I  loci  bne  30 1: 


.321 


i  J-'iTa  L.  -  -,:'.3;t  "u    ,  \; 

'<•/*'?•  4  o +  '•*     "^•^fc^•'^" 


16.  Methods  for  Increasing  the  Crop  Producing 

Power  of  Irrigation  Water--Widtsoe  and  Merrill. 
Utah  Agricultural  College,  Experiment  Station, 
Bulletin  118. 

17.  Studies  on  Capacities  of  Soils  for  Irrigation 

Water--0.  W.  Israelsen--Journal  of  Agricultural 
Research,  Vol.  XIII,  No.  1. 

18.  Investigations  of  the  Economical  Duty  of  Water 

for  Alfalfa  in  the  Sacramento  Valley- -E.  R.  Adams. 

19.  Report  on  Irrigation  Investigations  nn  the  North 
Side  Minnidoka  Project.   Harding. 

20.  Water  Requirements  of  Soils  in  the  Sunnyside  Valley 

Irrigation  District—Harding. 

21  Report  on  Irrigation  Investigations  at  Billings, 
Montana- -Harding . 

22.   Flow  of  Irrigation  Water  over  Soils  in  Different 
Methods  of  Application- -Harding. 

25.  The  Use  of  Water  from  the  Tuolumne  by  the  Modesto 
and  Turlock  Irrigation  Districts— Etcheverry  and 
Means . 

24.  Depths  to  which  different  Soils  may  be  wetted  by 

Irrigation  Water— 0.  W.  Isrelsen. 

25.  The_ Capillary  Movement  of  Soil  Moisture--W.  W. 

McLaughlin,  United  States  Department  of  Agriculture, 
Bulletin  855. 

26.  Annual  Reports  of  the  Reclamation  Service,  1912--1919. 

27.  Experiments  of  the  Economical  Use  of  Irrigation  Water 

in  Idaho—Don  H.  Bark,  United  States  Department  of 
Agriculture,  Bulletin  539. 

28.  Soil  Moisture  Studies  Under  Irrigation—Harris  and 

Bracken- -Utah  Agricultural  College  Experiment  Sta- 
tion, Bulletin  159. 

39.   Irrigation  Projects  Data— E.  A.  Moritz,  Vol.  9,  No. 
11,  Reclamation  Record. 


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.81 


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.  ^rl^-TiT    --aclctctoilqqA  'Io   sbotl^s./t 


rjoil  -jectsW  Io  es.U  siTT 
.^:  "eiG  no  i  .t*^iifsl   xcoliJjT  bne 


,  .;9.,9.,f  9c    . 

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—  21  «1 


CHAPTER  I 
INTRODUCTION 

It  is  well  recognized  that,  regardless  of  the 
crop  irrigated,  a  proper  knowledge  of  the  duty  of  water  is 
essential  to  both  the  Farmer  and  the  Engineer.  Such,  es- 
pecially, is  the  case  in  newly  developing  irrigated  and  ir- 
rigable districts.  With  the  growth  and  development  of  the 

0 

irrigated  sections  the  question  of  advantageously  and  eco- 
nomically using  the  limited  amount  of  irrigation  water  is 
becoming  more  and  more  apparent.  As  the  irrigable  lands 
become  more  settled,  more  frequently  is  it  asked  just  how 
much  water  is  necessary  to  produce  a  good  crop,  and  under 
what  conditions  of  irrigation  can  the  largest  returns  per 
acre  foot  of  water  as  well  as  pe  r  acre  be  expected. 

In  South  Africa  especially, in  its  present  period 
of  development,  is  it  essential  that  more  definite  informa- 
tion on  which  to  base  an  answer  to  these  questions,  be  ob- 
tained.  It  is  a  matter  of  extreme  regret  that  up  to  the 
present  no  experiments,  to  determine  the  water  Duty  of  our 
South  African  crops  under  the  many  varying  climatic  condi- 
tions, have  as  yet  been  undertaken. 

It  is  essential  to  the  farmer  and  irrigator  to 


lo   asslbifl^sT   .  -tar-d-  fossirsfooe-i  llsw  al  tfl 
ai  locfsvir  Ic   "^cfx/b   ec'-t  to   Qgbei^cni.  i^qc--iq  s    ^fcsct-s^liii   qoio 

-39   ,fiow2      ,i3srii,iii£i  aiict  bi:&  rf9rririB'>j.   srl«    xl^ocf  od1 
-ii  brtB  bsctjagiiTii  gciqolsvab  ^Xwsrt  nl   0aeo  axid1   ai 
sxi*  lo 

-oos  bitfj  Yia^cQ^fid-nsvbs  lo  rcoictaaup  srl^   enoJWaes  JJ 
ai  -iod;.8w  ncl.jB3iirii  lo   cj-m/ofon  bs^lmll   srW   gniaw  ^ 
a£>nx?I   aldB^iiiJ:   s/'uf   sA      .  ctaeiaqqa  SIOJB  •  bne   eiorvi 


tebror  .bxiB  ',qorio  Loorv^   aouboiq  o.t   Y~ssa3osn  ai 

•ioc  sni.^31  d  693^^1   siicf  HBO  nolJs^iiil  lo    anold'ibfioo- 

.bsdoec^xa  sJ  S-TOB  -i  sq  as   Xiew  SB  IS^BW  lo  c^ool  9105 
be  it       d-rfeaoiq  a-j  i  n^.r^-L210^^®  BoxilA  ii^efi  nl 
-aitnolnx   scf  inilsb  s-xont  d-Brf*   Icid-nsass  tfi  ai   tdroiuqclovab  lo 
-do   3or   ,  aaolj39JJp  seerld-  o^  iswsns  HB  as  •  ,-ioldvr  no  rscid- 

sx^  o-j    qu  Jsxid-   ;t9ri33'!   o^sictxe  .lo  fi:  rj   si  tfl      ..bsrxiBJ 

tcro.  lo  '^jyG  loijew  srf^  snim-  '        xs  on  Jaag- 

-tbnoo   pid-Birrilo   ^nlvr1^^  ¥&&&  ^  -'I3  naoiilA  xiv 


baa  -  OB  30  ax 


have  this  information  that  he  may  make  the  arrangement 
for  an  adequate  water  supply,  that  he  may  avoid  injury 
of  his  soil  through  the  application  of  too  much  water, 
and  that  he  may  adjust  to  his  land  the  amount  available 
to  him,  so  as  to  obtain  the  largest  possible  returns  per 

acre  foot  of  water  applied.  Further,  he  should  have  an 

of 
under standing /the  underground  movement  of  the  water  after 

its  application,  that  he  may  be  sure,  on  the  one  hand, 
that  excessive  losses  are  not  occurring  through  deep  per- 
colation, and,  on  the  other  hand,  that  the  irrigation  wa- 
ter is  penetrating  into  the  soil  sufficiently  deep  to  give 
proper  nourishment  to  the  feeding  roots  of  his  crop. 

It  is  essential  to  the  Engineer  to  have  such  in- 
formation at  his  disposal  in  order  that  he  may  determine 
how  large  a  canal  to  build  to  supply  a  definite  area,  or, 
having  determined  the  quantity  of  water  available  and  the 
cost  of  bringing  it  to  the  tract  to  be  irrigated,  he  could 
not  decide  upon  the  practicability  of  his  scheme  because 
of  his  inability  to  determine  how  large  an  area  the  water 
supply  is  able  to  serve. 

The  Engineer,  too,  should  have  an  accurate  know- 
ledge of  the  factors  that  influence  the  amount  of  water 


d7i9i::9  gneiss  erid    Q'Aan  *£Bm  eii  tfsitt  nold'amio'irii   aldd" 

biovfi  -sjjsm  9rf  tferfd1    .  ijlqqtfe  letfaw  stffiifpsbjs  IIB  tol 
jsw  rloxiTH  ood'  lo   nc/.o3CJcIqqs  grid1  jigxroidd'   lioa   sir!  io 


aidi^aoq  cJ-sssiBi   axfcf  rriacfcfo   oct   as   oa    ,miii 

rus  svsrl  blucila   a;i    (-is-dchritfi      .bsllaqs  rfs.t»w  Io   oool 

lo 

ij   lo   in9:,.avo;ri  bajjO'i^-iaL.'.;.    9         ^  •.'.";:.  .:J'L  ;  3  '': 

xl  ario  s;y  no  ,31;  /a  -3d  •%&&•  &&  ^Bitcf  ,  noli  JB  oil  qqs  aJi 
o'ir'j  yiliij/ooo  ooc  sis  asaacl  eviaaco.'.o  l-aifcf 
-aw  ncid-a^iiil  o^d"  j/saj  ,£>£isri  laxid-o  arid-  nc  -bas  -a 
vig  ocf  qsoa  ^XofiDioillua  Ixos  end1  o^£ii  gxiio^'icJ-onsq  si 

.qorio    a  In  io   aci-co'i  gnibosl   sricj1   o^  drxamfiaiixfor:  rioqoiq 
rcl   :,;ojya  avjezl  od"  issrii^n^-sii'd-  od  l^l^neeas  si  ctl 

n  gxi  $s:L-  riobio  ni  laaoqaib  aiif  ;ts  noictfir.^ol 
.B3rxs  sciini'lab  a  ^Xqqire  od"  bii0d  od"  iBnflo  B  93'i.el  won' 
£>HB  9lcfGllj8v«  'isd-sw  I'o  Tj^l^nBjjp  &d$  bsnliTrssd-ab  aniVBri 

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•  %• 

9axjBostf  sKtsifoa  aiii  lo  Y*-^--^30^^03'^?  d^  noqjj  sbioab  ^ort 
isdsw  eti*  asTB  ne  9316!  wod   =  '..ia'ani  aid  lo 

-    .  t   ©Ids   ai  T£iq 
worpi  ad'B'-iDOOB  HB   o  .  .  ,       '     ._£  orJT 

lo   r:         -  •  odoaz  ssij   lo    9? 


used  to  mature  a  crop  after  its  application  to  the  soil. 
Such  matters  as  the  spacing  of  the  furrows  in  orchard  ir- 
rigation, the  length  of  run  and  the  corresponding  most 
economical  head  of  water  to  be  used,  frequency  of  applica- 
tion are  of  vital  interest  to  the  success  of  an  irrigation 
scheme. 

Again,  we  shall  not  be  able  to  place  on  our 
statute  books  more  logical  laws  concerning  the  proper  use 
of  water,  or  to  enable  our  judges  to  render  more  satisfac- 
tory decisions  in  water  disputes,  until  we  have  gathered  a 
large  amount  of  data,  under  properly  controlled  conditions, 
relative  to  the  behaviour  of  water  when  brought  upon  soils 
for  the  production  of  crops. 

The  "duty  of  water"  is  a  phrase  which  expresses 
the  relationship  existing  between  a  given  quantity  of  water 
and  the  area  of  land  that  it  is  made  to  serve.   This  amount 
may  vary  between  the  wasteful  application  of  water  on  pre- 
pared lands  in  an  unscientific  way  to  the  highly  refined 
experimental  methods  as  used  for  instance  in  Southern  Cali- 
fornia, Where  according  to  P.  R.  Adams  "the  water  carried 
has  the  exceptional  agricultural  value  of  one  thousand  dol- 
lars per  miner's  inch." 


.Hoe   add  bd-  noJtd-jeolIgqa   a*!  isdlB  qo-xo   -3  oii^jsm  orf 

jci  awoiiul  arid-  lo  gnloflqs   slid-   a.s 
gnlbnoqasiioo  erfd'  bna  run  lo  xidgnal 
iiqqB  Ic  vons/fpsil   ^£>9au  ecf  o-t  isd-ow  lo  S 

i  na   lo   aasooua    artt  oi  d-asiodnJ:  Isd"iv  lo 


no   903lq  el   slcfs  9Cr  d"oit  Ilsxie   aw   «niBgA 

B.C-  laci^ol   9-io,it  asioocf 

Oi  oct   a93&i(t   'I00   ®Icfsn9  o*  10    ,/ied-j3w  lo 
ii  aiv  Ifdnxr   ,39-d-yqaiJb  rred-flw  r;i   anoi^Ioal)  ' 

q  isfenir   ,,  ed-sb  lo 
alloa  fioqu  drl^.uoid  neilw  is^sw  lo  i0oJ:VBii3Gf  arid- 

.aco^o   lo  ncldojyfcotq  siicf 
aesaatqxe  ifola'w  safi'iriq  B  el   "fis>;tsw  lo 
xod-Aw  lo  ^d-ld-iuawp  «9vl3  s  usswa-sc 

-niiOBta  aliffi      .evioa  oj  9.0  BHI  ai  dl  d-erid-  fcrtfil  lo  BSIS  edd 
-6'iq  nc  'lodsw  lo  rioictBDlIqq'B  l.olsJesw   3.ij   n          ocf  V1-07 
bs£iil9i  TjIiisM  9£fd  o*  -^sw  bilid03i»an0  JSB  nl  Bbasl  fi 
-iiaD  aiedd-jyoS  ni  sooed'snl  10!  t:  .  ;      a       .oond-sin  Isduamiis. 

W    Slid'''    8BU3&A     -S     -"5    O*  OOOS    ai9U>Y    ,BirftOl 

lo   e,  :oldqsox9  9£fct   a«ri 

la'1-  aisi 


4 


It  is  therefore,  in  order  to  be  more  definite, 
perhaps  advisable  to  use  the  phrase  "the  reasonable  water 

requirements,"  which  may  be  defined  as  "the  use  of  that 

.",'iat  by  e 
quantity  of  water  which  represents  good  practice  when  the 

character  of  the  soil,  topography  of  the  land,  value  of 
the  water,  crop  and  other  economic  conditions  are  taken 
into  consideration."  It  is  in  general  that  quantity  of 
water  with  which  the  average  farmer  should  obtain  the  best 

results  without  undue  waste. 

•••iJ.Cii  an  ir- 
It  is,  of  course,  obvious  that  this  quantity 

cannot  possibly  be  permanently  fixed  and  must  necessarily 
vary  not  only  with  the  physical  and  topographical  condi- 
tions under  which  the  water  is  applied,  but  also  upon  the 
economic  conditions  affecting  the  value  of  the  water  and 
the  resultant  crop. 

It  may  be  expressed  as  the  number  of  acres  that 
may  be  irrigated  by  a  definite  quantity  of  water,  usually 
a  second  foot  or  eusec,  flowing  continuously  throughout 
the  irrigation  season.   The  most "commonly  used  unit  is. 
however,  the  acre  foot,  which  represents  a  volume  of  water 
equivalent  to  a  depth  of  one  foot  on  an  area  of  one  acre. 

The  Gross  Duty  for  an  entire  System  is  made  up 


,  sdlrrilab  siom  sd  od  rtsbio  ol   te-so'i9'rorid-   ai  dl 


.     : 


arid"1'    as  bsiillsb  ac'    .  •     xioi.rfw  ",aJn3rii3-_ 

lct  nouw  eoi^os-iq  boog  •e^iiaasiqai  4o>nw  tad-jaw  lo  ^i^nawp 

3itf  lo  ijflqflisoqod1  »Iioe  orfd1  lo  nsJoaisnp 
t  3-iB  anoint  iDrroo  olirtonooe  isrlcto  £>HJS  qoio  ,'13-lsw  orld" 
lo  ^d-id-iiewp  ^snd-  I.eisri93  at.  8,1  W  "  .nold-aisblerioc  ochii 
cf  sxlit  nisd-do  blnca'a  isnTifll  ggaisva  arid-  xloitlw  u'dlvf  isdsw 


sJr.'id:  uB^io    ewoivoo    ,.  saitfoo  lo    ,ai 
n  ctawrsi  bns  baxil  Y-t;i'nsrism':£9Ci  9(^  ^ 

-Ibnoc   Ir;o.r:Iqj3risoqod-  brus  iBCie-jdq  &tii  dd"iw  ^Ino   don  *^^v 
grid  ncqu  oalB  dnd    ,&9llqqjs   ei  'isd^jsw  edd1  ifoliiw  leJbru;  aflold 
bits  'iodBw  arid  lo   saLav  orld  gnid-osllfl   anoidibnoo  olntoaooe 


a  91  os  lo  iscL-jm  ©ild  a^  L     .        ^a  oci  -^JSK 


dworf^wcirfd  •fclarrour  '  '  •  -1  bncog-j   a 

,  el   '  .  '        •  '        '  'figxiii  e 

e.:    -  ;  "  .....  ;OS     3/ld     ti:: 

• 
a:  --'•-.  '    .          -  :oiO  9.. 


of  the  net  Duty  and  the  Loss  in  transmission. 

The  net  Duty  represents  the  actual  amount  of 
water  delivered  to  the  land  and  includes  such  losses  as 
that  by  evaporation,  percolation  and  waste,  in  addition 
to  the  actual  amount  that  is  absorbed  by  the  plant. 

The  Gross  Duty  is  the  relation  between  the  to- 
tal irrigated  area  under  the  System  and  the  amount  of  wa- 
ter diverted  from  the  source  of  supply.   The  factors  that 
influence  the  gross  or  entire  duty  of  a  Scheme  are  as 
many  and  as  varied  as  the  conditions  under  which  an  ir- 
rigation scheme  operates.  An  attempt  to  summarize  all 
shown  in  the  following  table: 


ni  3sod  ailct  bna  'tfsjQ  $&n  srld1  lc 
lo   cfnifOffiB  Lsirtos   aJd-   ed-rtsesiqsi  Y«*&  cJ-grt  sal 
as   a323oi  rfox/a  asiu/IonJL  bns  bnsl    sifct  od  bari9vlle£» 

nl   t3oasw  bn&  nolctBlooisq    tnc.f.jjs'ioqsvo  Tjcf  d- 
q  9.ci^  ^jcf  bscfioads   a  I  JailS  driuoms  isxjd'Ofl   9ilj 
-ocf  9ilct  ns8wd-sd  noi^jsl.sri   9.ci^   ax 
lo   drii/onfl  9ilct  bnjs  ^scfaYS  erld- 

91  IT      .vlqqjLra  lo   301003   8iW  rrtorrl  bect'isvib 
3.3  ofi3  s.rteno^  B  lo  ^tub  s-ildrie  rio   03013 
-ii  HJS  iJoirlw  -isbrtL-  anoicf  Lbrioo   sri^   as  bei'-xsv  aa  b 

nA     . 

'i  9rid-  n±  nworfs 


(       (OJ        (Distribution 

(       ( 

• 

(Factors  (   .  f  ,  ,  (Quantity 
(       (Rainfall  (Distrlt)ution 

* 

(which   ( 

(Clear 

(can  be  (Water    (Fertilizing  silt 

(        (   carried  in  suspension 

(consid-  ( 

(         (Humidity 
vered  as  (        (Wind  movement 

(fixed   (Climate   fgggg?&  Irri_  ven  quantity  of 

(       (        (  gation  Season 
(Altitude 

(Losses  in  (Seepage 

(Storage   (Evaporation 

(         (          (1.  Distance  from  the 
i         i                j.        j-i   i   •• 
(       (                       stream  to  the  land 

(Losses  in  (          (2.  Soil  through  which 
(Transmis-  (&l         (    the  ditch  is  built 

(  sion             (S.  Kinds  of  (Lined  &  Unlined 

FACTORS 

(Factors  (         (          (    ditch  (Cross  Section 

(               ( 

INFLUEN- 

(which          (          (Canal 

(Evaporation(  Lateral 

CING  THE 

(may  be  (         (          (Field  ditch 

DUTY  OF 

(modified"        (Rotation  or  contin- 

(       (        (  uous  use 

WATER 

(Irriga-   (Method  of  applica- 

(  tion    (   tion 

(  Practice  (Head  used 

(       (        (Waste  water 

(Length  of  run 

( 

(Cultiva-  (Dry  mulch 

(  tion    (Ordinary  cultivation 

(Cover  crop 

(        (Configuration  of  Surface 
(Irrigable  (Soil  and  subsoil 

(  lands   (Reparation  of  the  land 

(         (Ground  water  level 

fcroos    (Length  of  growing  season 
(         (Diversified  or  not 

V 

(Factors (Faulty  adjudication  (Appropriation  and  granting 

flnrl  P.nm->+'.  Hvi^av»o    I    ~f  _.»  _i_j j 


(       (   and  Court  Orders 

(which  ( 

(may  be  ( 

(cor-    (methods  of 

(  rected(   payment 


-_  rights  to  more  water 
(  than  is  needed 

(Based  on  quantity  rate 
(Based  on  flat  rate 


•     .  - 
'jtfaJ  ) 


nc.~ 


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nc... 


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fi  3GCriO)    rfo-j-iJb          ) 


Jnl     . 
c,}  .a 


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CO^O     13VOO) 


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i  no  . 


All  these  factors  do  much  to  increase  or  de- 
crease the  area  that  may  be  served  by  a  given  quantity  of 
water.   There  remains,  as  a  disturbing  factor,  the  law 
that  the  more  water  that  is  added  to  a  crop,  the  smaller 
will  become  the  yield  per  unit  of  water  served.   This  law 
of  increasing  water  cost  raises  the  question  of  whether 

the  water  should  be  used  to  obtain  the  largest  possible 

50  acre  'Inches  'Yield  'Total  'Price  'Grose  '  t   M.et 

yield  per  acre  or  whether  moderate  quantities  shall  be 

used  to  obtain  the  largest  yield  per  acre  foot  of  water 
served. 

There  is  a  depth  of  water  for  each  type  of  land, 
crop  and  water  conditions,  which  will  provide  a  maximum 
profit.  When  water  is  added  to  a  greater  or  less  extent 
the  amount  of  profit  will  vary  accordingly.   It  is  only 
with  an  increase  of  our  knowledge  of  the  duty  of  water 
that  this  point  of  "optimum"  water,  or  of  maximum  benefici- 
al use,  can  be  determined  for  different  crops  and  climatic 
conditions. 

The  following  example  will  illustrate  this  point 
more  clearly.  (&) 

A  beet  field  is  supplying  beets  to  the  factory 
at  a  contract  price  of  five  dollars  per  ton.   The  total 
cost  of  producing  the  crops,  including  interest  on  the  in- 


-01)  'jo   sajsaionl:  od  rloim  cfc   2f£otfOB'i   939110    1IA 
lo  ySlSttBUp  nevig  B  ^d  £»sviea  ad  ~£am  Jfliid 

arid"    .lodoBl  gnidiLtfaib  &  a  3    .  arciamei 
r.e   add"    «qoio  B   ci  beabs   ai  d-BdJ  isdav;  siorci  arid-  d-jsifd" 
elriT      .&9visa  isdsv;  lo   dir/xr  isq  blsl^  sifd1   smooedllxv; 
isrid-QjiIw  lo  noidae-up  srld   aoa'ifl'i  daoo  'isd-BW  giiiaaoionl  "io 
sidlsaoq  dasgial   sild-  nlsdcfo  od  bsan  sd  bijjoxie  isd-aw  arid 
sd  IlBrfa   seidid-nsup  3d\srisbom  isrfd-aifv;  10 

o   dool   3-1  OB  i  aq  blc-l^  d-asgiBl   arid  niadco   od 


Ic   sq-od-  doss  iol  lad-sr  lo  ddqsb  B   ai 
irjjm'J:x.3fTi  B  abivciq  IIis,v  riolu'w   t  ano  id  I£mc  o  tedaw  br.a  qoio 
dnadxe  aasl  i-j  isd-ssis  a  od  bsibbs  el  isdav."  neiiW     .d-llo'iq 
^Ino   ai  dl      .YlsniE^eooa  -^isv  Uiw  diloiq  lo   dm/orris   add- 
^^dsw  lo  ^d;/5   sr!d   lo   egbslworal  IJLTO   lo   sasetonl  ns  rfdiw 
-ioilsnsd  murrixn-rr  lo  ^o    ,iedsw   "loxjircid-qo11   lo   dnioq  siiid-  dsad 
oidamilo  bnB   aqoio   dasisllxb   ciol  benxmisd-sb   ed  HBO    ,  aexr  IB 


d;nioq  aiad   sdBid-sx/ili  Iliw  .:g  gniwoliol 

. 
•'i'cd-ofll  arid  od  adssd  s^-  ;3   2-t  -A 

ladod   c  .nod  i9q   o  "  -•-•"   3  ; 

-rti  grid"  nc  '  '  ^^C0 


'  8 


vestment,  may  be  assumed  to  be  thirty  dollars  per  acre. 
Tabler  I  may  be  then  constructed  on  the  basis  of  the  crop 
yield  in  the  Utah  experiments  (see  Bulletin  115,  116  and 
117  Experiment  Station)  on  the  effect  of  varying  quanti- 
ties of  water  on  the  growth  of  crops. 


50  acre 
inches 
applied 
over 

1 

'inches  'Yield 
'of  wa-  'of 
'ter  on  'beets 
'each   'per 
acre   'acre 

'(tons) 
i 

T" 

Total  'Price 
yield  'paid 
of    'for 
beets  'ton 
(tons)'of 

'beets 
i 

1 

Gross 
in- 
come 
from 

beets 

, 

i 

Cost 
per 
acre 

:          J 

i 

To-  'Net 
tal  'in- 
cost  'come 
'from 
'beets 

i 

llet 
in- 
come 
from 
acre 

1  acre 

r 

30"   '21.0 
t 

21   '  $5 
i 

|105 

r 

$60 

i 

$  60'  $45 
i 

$45 

2  acres 
3  acres 
4  acres 

i 

15"   '19.5 
i 

10"   '18.6 
i 

7.5"  '16.3 

59   '   5 
i 

56   '   5 
,      i 

65   '   5 

195 

280 
325 

60 
60 

60 

'i     —  1 

120  '   75 
t 

180  '  100 
c    ' 

240'  85  ' 

37.50 
33.33 
21.25 

Prom  the  above,  it  will  be  seen,  that  the  largest  net  aggre- 
gate income,  was  obtained  when  the  30  acre  Inches  were  spread 
over  three  acres.  When  spread  over  more  or  less  land  this 
amount  decreased.   The  largest  profit  per  acre  was  obtained 
with  a  thirty  inch  application,  being  seven  and  one-half  dol- 
lars above  that  with  the  fifteen  inch  application.   In  the 
table  the  cost  of  the  water  has  not  been  taken  into  account, 


19 q  3i.3l lob  1*1  irf*   9tf  o*.  benttraea   ad  \;3;r;   t 
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baa  811    .311  aitellwH  $aa)    stfitemtiiaqxe  dad-Li  9di  at 

Ic  do ell 9   arid   no  AaoWa*3  ^nerfiittcqxa  VII 
Ic   ddviroig  arid1  •  ac  IS^BW  lo   3-3  id- 


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raoTtl' 

9'tOB1 


smo  o 

moil' 
ad29d' 


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83. 

SO- 


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a.9'i9a  ^ 


Jan  ctasaisl   3dd  osncJ    .ri^sa  ad  Xllw  d~i   <9vocfa  arid1 
si 9 '.T  aaxlonl  9'ioa  OS  eifd  rt9riw  banlsjcfo   asw   ,3i?too: 
ild-  brial   aaal  10  siorn  isvo  bJ39iqa  fiadtf     .as^oa  99ic!cf  -IQVO 
asw  8'ioa-/i9q  d-lloiq  dassial   9rfT      .ftdaaonosf)  i«iroras 
-Io&  llaxl-aao  bits  navsa  3ni9d   ^nold-aoilqqB  rloni'  ^d-ix 

.noWaolIqqa  danl  nse  tiw  d-arf*  svodfi  a-xsl 

oini  najiad  need  .ton  a-      i       i  r  arid  lo   iaoo  grid- 


9 


and  the  question  of  what  is  the  maximum  economical  yield 
will  therefore  be  dependent  on  whether  the  surplus  profit 
of  seven  and  one-half  dollars  will  compensate  for  the  cost 
of  the  extra  fifteen  Inches  of  water  applied.  Similarly 
in  the  fifteen  and  ten  inches  application,  the  maximum 
economical  duty  will  be  decided  on  whether  the  surplus  prof- 
it of  four  dollars  and  thirteen  cents  will  compensate  for 
the  cost  of  the  extra  five  inches  of  water  applied. 

The  differences  between  the  net  duty,  the  water 
requirement  for  maximum  per  acre  yield  and  the  water  re- 
quirement for  maximum  economical  per  acre  yield,  should 
therefore  be  clearly  kept  in  mind. 

"The  conect  water  requirement  for  maximum 
per  acre  yield  is  that  quantity  of  water 
which  is  necessary  to  produce  a  maximum 
yield  per  acre,  when  the  losses  of  water 
by  percolation,  evaporation  and  waste, 
which  can  be  controlled  by  skilful  meth- 
ods of  irrigation  and  cultivation,  have 
been  eliminated. 

The  water  requirement  for  maximum  econom- 
ical yield  from  a  limited  water  supply  is 
that  quantity  of  water  which  correctly 
used  will  give  the  maximum  total  net  re- 
turns from  a  limited  water  supply  and  is 
dependent  on  the  value  of  the  water,  the 
value  of  the  land,  the  cost  of  irrigating, 
the  cost  of  producing  the  crop  and  the 
value  of  the  crop.   The  net  duty  merely 
represents  the  volume  of  water  which  is 
used  according  to  the  available  water  sup- 
ply, the  judgment  and  the  skill  of  the 


blsJhj  laointofloos  ntoralxsm  O£»   al  cM££w  1o  no  id"  as  yp  anr*  frets 
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daco  arid  10!   acUansqj-noo  Illw  a-islfofc  llcii-eflo  brt^  nsvsa  lo 
.£>8ilqqs  is*  aw  Is   aaiioni  nss^'iil   eicfxa   artt  lo 
m  arid-   tnoWJ3olIqqs   asrfoai  ns*  fons  «0e*tll  eiij  nl 
£<y«ffl 

'iol  sd-sansqfttco  II  ivy   scfneo  aesd-'x         brus   sisllob  ^wol  lo  Jl 
.bsiXqqjB  iscfsw  lo  assort!  svil  BI^XS  sdd-.lo  d-aos  arid 
arid    .YJW&  d3a  sad- 
i9d-xjw  arid  5ns  biai^ 

9-1  os  i^q   leoinrorroos  mxBfiJtxam  10! 
.£»nJt:.i  nJt   dqail  \;Iis9lo  acf 


nujTilxfim  lo'i   d-n9m3rili/p9T:  -ledsA'  dooaoo 
i?jsw  lo  \;didfiEwp  datfd-    ai  blai^  S'loa  • 
tixefii  s  30i/I>oiq  od  ^saaeoon  el 

lo   aesaol   add  nauw   ,aioa  taq  fjlai\" 


-cfcrem  Iw'ilixa  ^d  bsllo-idnoo   ad  0ao  rfoirlw 
avsil   t 


rt'f 


•     ~    '3 '•:«?•"'  :  U  Jt)  . 

flmll   a  notl  &. 

io  Y;i 
. 

ei  bn«  ^laqws 
ory    . 

•       ' 


• 

.  319H1      .  • 

II  doJ 

'  ^  i 

' 


10 


Irrigator.  Where  water  Is  cheap  and 
abundant  throughout  the  irrigation 
season,  the  net  duty  will  often  exceed 
the  water  requirement  for  maximum  per 
acre  yield,  because  the  consequent  low 
price  does  not  enforce  careful  irriga- 
tion and  cultivation  methods.  Where 
water  is  scarce  and  therefore  valuable, 
which  is  the  usual  case  for  a  great 
part  of  the  arid  region,  the  net  duty 
will  approach  the  correct  water  require- 
ment for  maximum  total  economic  yield.  "(€>) 

The  amount  of  water  that  will  produce  the  largest 
per  acre  yield  of  a  certain  crop  is  by  no  means  at  any  time 
the  most  economic  Duty.  It  becomes  therefore  imperative  to 
undertake  sufficient  experiments  to  obtain  this  information 
for  all  the  standard  crops. 

Theoretically,  the  aim  in  irrigation  should  be  to 
obtain  the  highest  possible  efficiency  out  of  every  inch  of 
rainfall  and  every  supplementary  acre  inch  of  irrigation, 
and  to  use  the  least  amount  of  the  latter  necessary  to  main- 
tain a  favourable  moisture  content  throughout  the  main  part 
of  the  growing  season,  while  still  permitting  the  soil  to 
dry  out  sufficiently  to  mature  the  crop.   Irrigation  should 
be  applied  when  the  soil  moisture  content  drops  to  near  the 
wilting  point,  and  in  just  a  sufficient  amount  to  raise  the 
moisture  content  to  the  maximum  usable  water  capacity  of  the 
soil  throughout  the  root  zone. 


bos  qssifo   al  i 

noWaai'rxi  9rfd  d-jjoifcjjjciild-  dnabaxjda 
gsoxs  hed-lo   IlJw  T#JJ6  don  siid    <noe392 
isq  nuralXBrtt  ic'i   driameiiwpsT:  isdsw  sdd 
wo  I   dngupgonco   arid1   ascreoadF   «5l9l^  eios 

las  ion  secb 
Jtd-evld-I.t/o  fta 


9r£cl9ji3f-d'  brrfl 
^;   s  -iol   saeo   lauaw  sxit   al 


I9>i«w  d-osi'ioo   eri*  rfosoiqqa 
olmonoos   lactod"  nLurnixsrn  to'l 


o'iq  II  lw  -**dcr  ted-aw  lo   d-ax/oms  erJT 

d-a   arrasm  on  ^d  a.t  qoic   nlad-ieo  JB  lo  blsx^  910.3  13  q 
oj   9Vld-Bi6q«iJt   9101919^   39aoo9cf  *I      .  ^ojjQ  •  olmoaoos  cfaont 
airid  nl^tcio   o^   ^JHami^sqxs   d£t9ioJtllua   gaiadi 

.aqorio  bi»3ijnBd'3   sxi-J 
9d  bli/oda   noid-asliil  nx   ^is   srid    rtfllaoxc^oeriT 

1p   ;tuo   YO«9i°i'3t'1®   slcfJtasoq  daadaix;  axid  rtlflddo 
lo   rioni   9-ros   ijiB^nsmel  qq.ua  ^isvs   OHB   ila'iriis'i 
-nJtsm  od"  11BE390S0  isdd-dl1  9iid   lo   cto/ohta   dsasl  erld-   oau 
iiaq  niaw.  »ri*   Jijor^o^r^   Jnsdaco   9*ruJai'oio  alda»ti«)Vfll 

od-  lioa   9dS  jjnijdiimtsq  lllda  ellrfw   vi,  gnlwois  9£l: 

blwoxia  notd-esliil  •  ,   .<JP'io  add-   etufBin  od  •  \          '  olllwe  dwo  - 
9£{d  ia9a.  od  sqoib  dast^mo  etwdaiaia  II  neriw 


arid  lo  ^dlaaqao  ts^aw  o*  *B^ftps   aiwteion 

•r  erJ      :*•!.•  lioe 


11 


Proper  irrigation  supplies  a  favourable  moisture 
condition  and  encourages  the  growth  of  feeding  roots,  bac- 
terial activity,  and  the  liberation  of  plant  food.   Im- 
proper irrigation  checks  these  processes  and  often  causes 
unfavourable  soil  temperature  and  drainage  problems,  or 
the  leaching  of  plant  food.   Proper  irrigation  tends  to 
produce  optimum  moisture  content  conditions.   Again,  there 
is  always  a  tendency  under  irrigation  to  compact  the  soil 
and  to  exclude  the  air.   It  is  exceedingly  important , there- 
fore, to  practice  rotation,  including  soil  building  crops 
which  will  offset  this  tendency  of  the  soil  to  compact  and 
make  it  practicable  to  maintain  a  high  state  of  tilth  with 
a  high  percentage  of  organic  matter.   It  is  the  intention 
to  discuss  in  this  thesis  these  influences  which  may  modify 
the  net  JXity  of  water,  rather  than  the  many, varied  and  com- 
plex factors,  enumerated  above,  which  go  together  to  form 
the  Gross  Duty  of  an  Irrigation  System. 

That  it  is  well  worth  our  time  to  give  careful 
study  and  investigation  to  this  particular  phase  of  the 
question  is  b  orne  out  by  the  following  general  figures  of 
the  disposal  of  irrigation  water  after  its  application  to 
the  soil. 


II 


slcfaii/cvsl   s  asllqqi/e  uoi3&%±rii£ 
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nsi'io  £>n.3  aaaaeociq  sasdd-  a^ioado 

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nol-te5irrti  Taqo'rl      .boo'i  cfnalq  lo 

.snoid-Jtbnoo  ^nsvincc   siwctaiom  miflRid'qo  SOJJDO-ICV 
Iloa   siil   dottqinoo   oi  xiol-tsali'il  i^bnx/  ^onsDnad' .  a   a^jswla   ai 
^Ignlfiaeox-i   al   ctl      .'xia  arW  ebuloxe  ol  £>nB 
Ilca   ^riibji'Ioni    tKoid'ScJ'oi   soidosiq  o;f    .910! 
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lo    3d -Su   d'oia.  s  n.£a.jnicra  oJ  slcfao.ttooiq  ctl    s^lBfli 
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ifoiiiw   ssonsullni   assrll   alasriit   airi^  ni   adooaio  oct 
moo   .bna  JjsJ-rjBVi^msm  e^Ict   naa^  isactei    tri3»t9\7  ic  ^jwd-'^sn  ©d^ 
tiriol  ol  i^£ii 330.1  og  iicl'flw   ..  9voo^  Jb3o  oisnujns    ta^ipd'os'i  xalq 

.:«9^aY2  nolcrasi^nl  ne  'lo  ^ud  aaoiD  srlci 
liria'iao   svi^  oo'    & ••(:!*  11/0  £[^*iow  Ilsw  al  .^1   **£lT 
srf*  lo   easrlq  islsjQlitaq  airfj-  od1  rcol-tngi739vni  £>as 

*.-  ' '  -7 

lo   ssiw^il  laisnas  si^lw'ollol  9^  •  orrio  cf  ei  ricW 

od1  noid'sollviqs  adi  ^ect•la  isdaw  .  -ri   lo   laaoqalJD 

.a 


12 


Surface  waste  5-  -15  percent 

Deep  percolation  losses  20--50 
Soil  evaporation        10--20 

Total      "   S5--85    " 

Amount  available  for 
plant  transpiration    65--15 

It  will  be  seen  that  even  under  the  best  of  conditions, 
the  losses  will  usually  amount  to  thirty-five  percent  of 
the  water  applied. 

"While  these  losses  appear  high  and  while 
they  can  be  reduced  under  proper  methods 
of  irrigation,  the  expense  of  their  re- 
duction may,  in  many  localities,  exceed 
the  present  value  of  the  water  saved. 
Where  the  losses  are  excessive,  the  best 
crops  are  usually  not  secured  and  it  will 
pay  to  improve  the  method  used  and  reduce 
the  losses  to  reasonable  amounts,  " 


Whilst  it  is  unquestionable  that  the  major  part 
of  this  loss  is  due  rather  to  the  mechanical  factors  of 
the  application  of  the  water  to  the  land—factors  which 
even  under  the  very  best  of  conditions  are  often  not  prac- 
ticable to  modify  —  a  greatly  increased  efficiency  of  the 
water  should  be  obtained  from  a  proper  knowledge  of  the 
more  theoretical  considerations  of  the  question.   It  is 
rather  with  this  part  of  the  problem  to  which  this  discus- 
sion will  be  limited.   Any  improvement  on  the  practical 


21 


•jrreoisq  SI  —2  sctss?/ 

03-  -OS  aaeacl  col;*J8lqo«jsq  qegtl 

QS—  OI  noid-3'£oqsv9   Iio3 
38-  -32 


51  --co 

,aao  loir-no  c   "io   craed  Silct   -isjsm/  nevs 
"to   ^nooiLi    •»vll-\d'-ix;:fd'   o~  ^xu/oma 


ici  D^cfsllayje  tauiom 
fioi^/Jtlqanarict  j-fislq 


ness   sd  II  lw  d~x 
IIlw  -aoaaoi   sdcfr 


ell.iw 

afcon/sw 

-o-i  'li 


aaaaol 


io 


Iliw 


< 


9ciii  saeaol   aiij    e'i. 
Liw  f>ociwos.fcj    ton  ^Il3.ua;;  '913   aqoio 
I>nB  bsau  ho;iy&m  Siitf   avoiquti  p^  x 

o^   asasol 


lo 


artcoOB'l--f)ruI  srW   o-l 
xq  uO0  ns-Jlo   SIB    aitold-lBiic 
*  lo    ^oneioills  fosaasioci 
lo  s;^I)9iwonji  igqciq  a 


ewb  a.t    aaol   airict   'Io 
lo  noWfioilqqs  srid- 


nsve 


ai    \t  •  no  Ji  j  2  9  l.fp    9ilo        o     QfiC 

u*  rfo!4»  od-  msldoiq  a 


SIOQflj 


sq  aMcf  rCcfiw 
9JliKil  sd  Iliw  coia 


13 


side  is  an  entire  local  question,  to  be  solved  by  each 
individual  project  according  to  the  prevailing  conditions, 
A  discussion  of  this  side  of  the  question  could  at  the 
very  best  only  be  most  indefinite.   On  the  other  hand 
theoretical  considerations  lead  to  definite  principles 
which  if  followed  expeditiously  should  help  to  secure  not 
only  a  higher  increased  Duty  on  existing  schemes,  but  al- 
so give  much  more  definite  information  as  to  the  probable 
irrigable  area  under  a  projected  scheme. 


rioss  TO'  bavioa   od  od"   tnol;ra9up  laoql   atlctna  «B  si 

9-cW  o*  p  i63(,oiq 

MX/CO  noid'asi/p  9ji*  lo  s&la  aiitt  lo  Hc 
tsrSto  sif^  nO      .stinllsbni  *aom  ad  Tjlno  cfaecf  -^ 

beal   anoictB^sfiisnoo   Isold'9>' 

ten  sijjosa  o^   ql.»ri  bIifOB'3  ^awoWlfisq^s  bewollol  li 
-Is  cl-t/d    tastaeiloa   3ni--tax>:e  no   Y*^  baafleioni  isrigM  a 

9iCct  o*  as  xiold-sfmolxil  acHnll-^b  siosi  ilown  svig  os 

s  ri  >s 


14 


CHAPTER  II 

•    •.  -  i»  <*'.•.«%  vvr  i»      »rc,  v>-  • .  J  •,••      •>  *  7<       "-'  •  .-..  •        r-  T  •     '   -.  *  f- 

THE  TEXTURE  AND  STRUCTURE  OF  THE  SOIL 

It  is  now  perhaps  universally  recognized  that 
the  character  of  the  soil  has  more  influence  upon  the  Duty 
of  water,  in  the  sense  of  the  reasonable  water  requirement, 
than  any  other  factor.   It  is  the  texture  and  structure  of 
the  soil  which  to  a  large  extent  determines  the  amount  of 
water  that  is  lost  by  deep  percolation,  carrying  with  it 
below  the  root  zone  a  considerable  amount  of  valuable  plant 
food.   It  is  also  the  texture  and  structure  of  the  soil 
which  determines  the  lateral  movement  of  the  water  for  equal 
distribution  under  furrow  irrigation,  as  well  as  the  upward 
movement  with  its  consequent  evaporation.  A  brief  survey  of 
some  of  the  importance  characteristics  of  soils  will  help  in 
obtaining  a  clearer  perspective  of  the  various  influences  to 
which  irrigation  water  is  subjected.   Arbitrarily  speaking, 
soils  may  be  divided  into  seven  grades  or  "separates",  com- 

'-'"--•;     i   •'  -  "X  .  . 

prising  fine  gravel,  coarse  sand,  medium  sand,  fine  sand, 
very  fine  sand,  silt  and  clay.   This  grouping,  established 
by  the  United  States  Bureau  of  Soils,  is  dependent  on  the 
size  or  tecture  of  the  soil  particles,  varying  from  2 — 1  mms. 
in  diameter  for  fine  gravel  to  diameters  below  .005  mms.  for 
clay. 


II 


lo 
"10 

cf-1 


JIGS  3H1 

ld-  beslnnoosi  -\jIlBai3  vim/  aqsitaaq  won  al  d1! 
•^d-wCI  arid-  noq>  soaewllnjt  a'xora  BBC!  lioa   srfd-  lo 

3idBnoajS9Tc   &d3  lo   eartsa   exio   nl    ««i9ctaw  lo 
iudxscf   srij-   ai  *I      .lod-oal  isacto  Y^B  aadcf 
sill  a9nl«w9*efc   J-JisJze  s^isi   s  otf  rlolrivr  lioa  sad- 

qeeb  ^cf  tfsol.   al   rfsrld-  ri^-3v/ 
a  snos  d-ooi  add1  wolod 

lioa    5:id   lo   3'i.udoxnd-e  Jbn-c   9i.ad;x8d-   sifd-  oals   ai  .i>coi 

tol  T9d-.3w  slid-  io   d-nsmsvom  Isisd-sl   eif*   asnim-isd-sb  £foiil\v 
i;  3/ict   as    Ilav 
lc   Y9\nua  Isiid  A 

ni  qisri  Iliw  alio^  lc 
oct    aaonswllni   awclisv   erid-  lo    9Vjd-o3 

..^niaiaaqa   ^Il'ia-itlcTiA      .bs^oaccfi/a   ai   -tdd-s-J   iroW33±Ttl  xfolri* 
-moo    ^'as'ts-ieqaa"   10    asbBta  nsvse  od-ni  bscivlp   sd  Tfsrr  silos 
.&JXSB  anil    «bnB3   miribsftt  .,bnjaa  saiBOO    ,l9VBis   snil  tin 

'  JXla    *&rt*e    snn 


v;ofirii;'i 


90C08d--ioqmi   add    'ic    srrtoa 


rto 

a,Tjrt  1  —  2  moil 
10! 


ei    , 


lo 


f  air 


ull 


15 


As  these  groups  vary  in  size  they  exhibit 
properties,  especially  in  regard  to  the  moisture  content, 
which  vary  widely,  which  again  are  imparted  to  the   soil 

V   1  ,.\      ;-'---••  f",  '•'    ,       <~ 

of  which  they  are  members. 

These  clay  particles  are  very  minute,  jagged  and 
angular  in  outline.   They  are  highly  plastic,  and  when 
rubbed  together  become  sticky  and  impervious.   They  shrink 
on  drying  and  re-expand  on  being  melted.   The  finer  part 
of  the  clay  consists  of  colloids,  which,  because  of  their 
fineness  of  division,  exhibit  certain  well  defined  proper- 
ties, of  which  absorption  of  moisture  and  high  plasicity 
and  cohesion  are  the  most  important.   Silt  exhibits  the 

V' '   ;  i  <;   •   '.  •  ••  'i  .:•  ':•'• 

same  qualities,  but  to  a  much  less  marked  extent.   The 
presence  of  clay  imparts  to  it  a  heavy  texture,  with  a  ten- 
dency to  very  slow  water  and  air  movement.   Its  water  hold- 
ing capacity  is  high.   The  soil  is  highly  plastic,  becomes 
sticky  when  too  wet  and  hard  and  cloddy  when  too  dry. 

The  sands  and  the  gravels  function  more  as  separ- 
ate particles.   They  are  irregular  and  rounded,  exhibit 
very  low  plasticity  and  cohesion  and  as  a  consequence  are 
little  Influenced  by  changes  in  water  content.   Their  water 
holding  capacity  is  low,  and  because  of  the  large  individual 
size  of  the  pore  space  the  passage  of  water  is  rapid.   In 


esia  at  Y 

<*ri9;tiioo  siirtaiom  ertf  o* 
Iloa*    eil*  o*  b3*-ieqmi  9ifi 


-blorl 


fens    «oi^afilq 


aquoig  saarf*   sA 
nl  ^Ilaxoeqas    <ss  W 
riolrfw   ,^Isbiw  Ytav 
i  arts 


cl 


•4 


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55flll9l>  ilow  ftJ 

rigirl  barf  sv' 


•:S 

1*3     9:TfCO 

no  im.3qx©-9*x  bita  sptTtb 

*idMx©    <fto£alvxb  lo   a  a  or,  on  il 
'io  nox*qio8cfs  doJWj?  lo    .331* 


11-',?^  3281  ilojjra  s  o*  *trcf  ,aax*ll30p  •  rstea 
1-^  ,  9itr*X9*  Y^3®1''  B  '-'"^  °;:!'  s*%eq;ftl  ^slo  lo  eonsao'iq 
3'/r  3*1  .*ri3ittevcni  ils  bit-?  ie*BW  wola  TJTTSV  o* 
.oWasIq  ^I;.i3^I  ax  ixcs  sdT  .dslii'a.i  .  5 

t  risriw  T^bbolo  Jbfls   5*iBi{  bite  *9tf  oo* 
o'iofn  noiioayl  alaivsig  sxi*  5xis  abrtsa  9d 


wo  I   vi-sv 
eX**ii 


9on9.vpsanoo  B   32  bne  aolas 
ilsiIT      .*nad-n:oo  is^sw  at 


16 


regard  to  structure-- or  the  arrangement  of  the  soil  par- 
ticles in  the  soil--a  wide  variance  is  met  as  well. 

It  is  a  well  known  fact  that  the  soil  particles 
are  not  homogeneous  in  size;  neither  do  all  the  particles 
function  as  simple  grains ,  being  gathered  together  in 
groups  called  granules  or  crumb  structure.   A  small  particle 
of  soil  may  be  made  up  of  a  number  of  very  small  grains 
placed  in  between  somewhat  larger  particles,  resulting  in  a 
reduction  of  the  pore  space.  A  soil  having  such  restricted 
pore  space  is  said  to  be  in  a  puddled  condition.   The  condi- 
tion is  detrimental  to  plant  growth,  impeding  the  root  de- 
velopment, but  also  preventing  the  circulation  of  air  and 
water;  a  most  necessary  function  for  plant  growth. 

On  the  other  hand,  when  a  soil  is  made  up  of  com- 
plexes of  soil  granules  an  increased  pore  space  will  occur. 
There  will  therefore  be  a  very  wide  ranpe  of  pore  space  rang- 
ing for  the  different  types  of  soils  as  shown  by  Table  II. 


Ixoa   ertt  lo   ^nanissnsiis   arl*  io--srii/o  o.uid-3   o;t  £13391 
tf  as  d-3iK  al   sonslisv   sblw  js--lioa   s-ctt  ni   ee 
Xloa   srict  cterfcf   d-osi  riworui  llov/   e   al  d"i 
exld    IX s  oi>  iferWisn   ^e^ia  «1  a.uosnsBpmori  cton 
nl  i9d*9aod-  Bs'isrictag  ^iiierJ    « aixisi^  slqinls   aa  nol^ 
q  Il^i'ta  A    "  .0'iwd-o.tn ia   cfnujio   rio   asiynsig  Jjsli.30  jqijoig 
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l£>noo  oiTI'      .ncinifjnoo  boXM)jJc     s  nl   sd  o*  biea   a  I   9-0  aq  a   8-ioq 
-8b   d-co'i   3iicf   ^il&sqrai    ,Tl*woi-^  itrwlq  oi    Xa^ng^l'id-ob   a  I 
bna  iii  io   nol,-t.ai00TJ.o.  e:i^   3fil*rj9V9iq  oaXa  ^twcf   ^^nam 

.rld-vroi^  :trt>3lq  -iol  noi*oitJ/i  Y1^aasosxi  ^-°M  s    l^9 
-;uoo  lo  qjj   9&o.E  al   iica   B  nsrlw    ,£»nsi£  isrid-o   arid  n-u 
.T:.UOOO   XXI. v  aosqe   9ioq  tsa^a-ionl  HB   aaXi/nais  lioa    i 

soaqa   yioq  io   9-;,ftfli  afcl'w  ^sv    a   9tf ' sip'lsisri*   XXlw 
.IX  aXdai'  ^d  nwoiia   aa   aXioa   lo   asq"^*  dnsialllt)   9.1; 


17 


TABLE  II    nt. 

Percentage  of  Pore  Space  for  Different  Soils 
(King) 

Sandy   soil  52.49 

Loam  54.49 

Heavy  loam       44.15 

Loamy  clay  soil  45.52 

Clay  loam        47.10 

Clay  48.00 

Very  fine  clay   52.94 

The  pore  space  in  any  of  these  soils  is  natural- 
ly subject  to  considerable  fluctuation,  especially  in  the 
surface  soil,  due  to  tillage  and  the  amount  of  organic 

matter  present.   When,  however,  soils  are  in  the  physical 
•.iota  lr..ar<st*fcd  grant:  *-,-  :icu.  "  &ac  -'-.:oe  tin 
condition  for  the  best  plant  growth,  it  will  be  found 

that  the  finer  the  soil,  the  greater  will  be  the  pore 
space. 

In  a  soil  the  pore  space  is  occupied  by  water 
and  air.   If  the  water  content  is  low,  the  pore  space  is 
large  and  vice  versa.   Thus  the  relationship  of  the  aggre- 
gate pore  space  and  the  size  of  the  individual  spaces  to 
the  amount  of  contained  air  and  water,  to  their  movement 
through  the  soil,  to  root  extension,  to  soil  aeration,  to 


II   iLldAT 
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» 

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i^v;Tc    D-"   ni   01^   slxoa    fi3V9»rcrr  ,  ne^iW      .^naagtq  Ta^J-^jtr 

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svom  ilgiicf  oct    ^is-lsjif  ixct?  iJts  b.sol  s-i  no  r: 
.rtoId-siaB  lioa  o^   ,nolsrt9jjt;©  ^001  oJ   ,llo,; 


18 


bacterial  activity  become  apparent. 

The  factors  which  control  the  soil  structure 
are  plasticity  and  cohesion.   As  these  increase,  there 
is.  with  an  excess  of  water,  a  tendency  towards  puddling. 
Oh  the  other  hand,  when  too  dry  clodding  will  result.  'A 
diminution  of  these  factors  in  heavy  soils  will  give  a 
better  granulation  of  the  soil  particles. 

Granulation  is  "nothing  more  or  less  than  a 
condition  brought  about  by  the  force  exerted  by  a  variable 
water  film  and  the  pulling  and  binding  capacities  of  col- 
loidal matter,  operating  at  numberless  localized  foci.   It 
is  evident  that  any  influence  or  change  in  the  soil  which 
will  cause  a  greater  localization  of  these  forces  v/ill  pro- 
mote increased  granulation."  And  since  the  optimum  moisture 
condition  of  a  soil  for  tillage  is  also  fortunately  the  op- 
timum condition  for  plant  growth,  careful  attention  should 
be  paid  to  the  effect  of  alternate  wetting  and  drying  of  the 
soil,  ploughing,  freezing  and  thawing,  and  the  addition  of 
organic  matter  and  lime,  upon  the  granulation  of  the  soil 
particles. 

The  moisture  contained  in  the  soil  may  be  hygro- 
scopic, capillary  and  gravitational.  Hygroscopic  moisture 
is  the  moisture  which  a  soil  dried  by  artificial  heat  will 


81 


snoosd  ^cMvj-^ofi   laliectocd 
'S   lice  erlj   Ici^aop  rlelrlw  a-iotfojel  snT 
saje'ionl   s^aii*   sA      .nclaerlco  bits  Y^-^-^BBlq  9is 
abiewoci   Y3^9-0-0"9^   8    «is*aw  lo   aascxo  ns  riiiw    .3! 
A'    .^Iwas-r   jil-w  grijb£>clo   Y*I^  cod"  asdw   ,  firxsrf  isn'^c    9r&   nO 
a  BV  1%  liJtw  aiioa   ^vesa  ni   aic^osl  sascid'  lo  rtolJwnJtfaib 
.  :;9lol.iisq  lios   exit  lo  no  Id-  si  was  135  isJiscf 
s  rxB/iT   aa?i  -T:C    9rrcin  j^nliid'c 
lcfalisv   -3  ^cf  te^iexe   aoicl   srfd- 
-Ico  lc   a-:'i^iojsc30   jjnibxil-:-  br.a 
l      .loci  I)9slleocl   8asici3CJnwn 
;Ioxa.v  Uou    srit    al   s^nsrio  10 


al 


ed*  bas  mill  'io^aw 

..'is 
Jaxtf    JneoiV3   ai 


IIlv;  ^Vc 

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lc   ncl^lbba    9iIJ  boe    t  get  1  wad*  boa  gnisseil    .  ^clils^olq 

I  lea   oiIJ  lo  floijolirnana  arid  noqjj   1  9  ml  I   bna 


ni 


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,olqo-oa 


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rfelilv?   a^        '    ;n  srfj   a 


19 


absorb  from  a  saturated  atmosphere.   Due  to  the  absorptive 
capacity  of  the  soil  particles,  this  moisture  will  exist 
round  the  particles  in  the  form  of  a  thin  film,  being  held 
partly  by  the  surface  tension  of  the  film  and  partly  by 
the  molecular  attraction  of  the  moisture  molecules.   The 
amount  of  hygroscopic  moisture  increases  with  the  total 
surface  exposed  or  the  fineness  of  the  particles.   Any 
practice  that  will  increase  the  colloidal  material—the 
humous,  colloids  being  very  susceptible  to  an  increase-- 
the  higher  will  be  the  percentage  of  hygroscopic  moisutre. 
This  is  well  illustrated  in  Table  III. 

TABLE  III 
Hygroscopic  Capacity  of  Various  Soils 


Soil  Percent  clay  Hygroscopic 

remaining  in  Water  ex- 

suspension  pressed  in 

after  stand-  percent 
ing  24  hours 

15  clays 

7  clay  loams 

9  loams 

5  sandy  loams 

4  sands 

Hygroscopic  water  is  held  so  rigidly  to  the  soil  particle 
that  it  is  in  no  way  available  to  the  plant.  As  this  zone 


51.97 

10.45 

17.15 

6.06 

12.06 

5.18 

7.39 

2.50 

2.95 

2.21 

61 


IX  iw 
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iBoioIIoo  add"  easeionl  IlJt*  <tfijrf^ 
aa  o3    eldid-qsoai/E   Y^ev  iolloo    ^aoorritrxl 

iri  oJ:qooco'ig^fi  lo  eafi^nsoieq  c-  XII.',1  taxlglrl  orf.^ 

.lli-oldisT  nl  i>e^B^»jj!Il   Hew  si   alriT 
III  3JHAT 


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S&.OI 

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20 


increases,  due  to  an  increase  in  the  moisture  content,  a 
thickness  of  moisture  film  is  reached  in  which  the  molecu- 
lar movement  is  perfectly  free  and  unimpeded.   These  two 
zones,  one  in  which  capillary  movement  is  more  or  less 
free,  and  the  other  a  comparatively  thin  film  in  which  molec- 
ular movement  keeps  the  moisture  attached  to  the  soil  parti- 
cle, gradually  merge  into  one  another. 

As  more  water  is  added  and  the  film  thickness 
round  the  soil  grains,  the  outer  layers  are  held  with  de- 
creasing force,  and  a  point  is  reached  at  which  plants  are 
able  to  procure  all  the  moisture  needed.   At  this  point,  ac- 
cording to  Dr.  Widtsoe,  the  film  water  is  held  so  loosely 
that  it  moves  freely  from  soil  particle  to  soil  particle, 
being  termed  the  Lento  capillary  point.   Above  this  point  the 
water  is  readily  available  to  plants  and  constitutes  the 
main  supply  of  water  for  plants  under  irrigated  conditions. 

Hence  the  following  coefficients  are  well  estab- 
lished (1)  The  hygroscopic  coefficient  is  the  percent  of 
moisture,  based  on  the  dry  weight  of  a  soil,  that  a  dry  soil 
will  absorb  when  placed  in  a  saturated  atmosphere.   (2)  The 
wilting  coefficient  is  the  percent  of  moisture,  based  on  the 
dry  weight  of  the  soil,  which  remains  in  the  soil  when  the 
plant  has  reached  a  condition  of  permanent  wilting. 


OS 


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21 


For  successful  plant  growth,  the  moisture  con- 
tent should  never  be  allowed  to  approach  the  wilting  coef- 
ficient.  According  to  the  researches  of  Briggs  and  Shantz 
the  hygroscopic  coefficient  is  about  .68  as  great  as  the 
wilting  coefficient  or  the  wilting  coefficient  is  about 
1.50  times  the  hygroscopic  coefficient. 

The  finer  the  texture  of  a  soil,  the  greater  is 
the  number  of  angles  between  the  particles  in  which  a  film 
of  capillary  water  may  be  held;  also,  the  actual  amount  of 
surface  exposed  by  the  particles  is  immensely  larger  than 
in  a  coarse  soil.   Due  to  these  two  conditions  a  soil  of 
fine  texture  will  contain  considerably  more  capillary  water 
than  one  of  which  the  texture  is  coarse.   See  Fig.  I. 

The  structure  of  the  soil,  or  the  arrangement  of 
the  particles,  will  become  a  factor  in  the  capillary  capaci- 
ty in  so  far  as  it  affects  the  amount  of  surface  exposed  to 
capillary  action.   Hence  the  granulation  of  a  clay  soil,  by 
producing  a  crumb  structure  and  by  increasing  the  exposed 
surface,  tends  to  increase  its  water  holding  capacity.   On 
the  other  hand  the  compacting  of  a  sand,  by  increasing  both 
the  effective  surface  as  well  as  increasing  the  possible 
number  of  angles  for  capillary  concentration,  will  have  the 
same  effect.   See  Fig.  II.   Organic  matter  has  a  great  capil- 


- 

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22 


lary  capacity.   Not  only  its  porosity  but  also  its  col- 
loidal content  exerts  a  very  high  affinity  for  capillary 
water. 

Capillary  water  moves  from  a  wetter  or  thicker 
moisture  film  to  a  drier  or  thinner  water  film.   The  water 
will  rise  to  a  greater  height  on  a  fine  textured  soil  tham 
on  a  coarse  textured  soil,  although  its  rate  of  progress 
is  much  greater  in  the  latter.  Lyon  and  Pippin  give  the 
following  Table. 

TABLE  IV 
Capillary  Rise  in  Inches  for  Different  Lengths  of  Time/^/ 


1 

Soil   |$  hr 

1  hr 

1 

2  hrs 

r 
1  day 

3  days 

3  days 

13 
days 

19 
days 

Silt  and 
very  fine  ' 

sand     '2.7 
i 

4.7 

7.0 

20.0 

30.0 

45.0 

52.0 

56.0 

Very  fine  ' 

sand     '7.6 
i 

10.0 

12.4 

21.0 

23.0 

26.0 

27.5 

28.5 

Pine  sand  '9.0 

i 

9.5 

10.0 

11.6 

13.0 

14.3 

15.2 

16.0 

Coarse    " 
and  medi-  ' 

urn  sand   '5.8 
i 

6.0 

6.3 

7.5 

9.0 

10.0 

11.5 

t 

12.5 

Fine 

gravel    '4.0 
i 

5.0 

5.3 
i 

6.4 
I 

8.0 

9.0 

10.0 

10.8 

22 


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With  a  further  increase  in  the  water  content,  a  point 
will  be  reached  when  new  additions  of  water  will  simply 
slide  off  the  existing  film  and  be  drawn  off  by  gravity. 
Dr.  Widtsoe  has  called  this  point  the  point  of  maximum 
capillary  capacity.   Any  existing  water  above  this  is 
termed   Gravitational  water.   See  Pig.  III.   It  moves 
slowly  downward  through  the  pores  and  tubes  of  the  soil 
until  it  is  all  absorbed  by  the  lower  drier  soil  or  until 
it  communicates  with  the  standing  water  table.   When  gravi- 
tational water  begins  to  appear,  an  adverse  condition  to 
plant  growth  is  obtained.   The  proper  aeration  oi  the  soil 
is  much  hampered,  the  roots  are  deprived  of  their  oxygen 
and  toxic  materials  tend  to  accumulate.   It  is  therefore 
evident  that  there  must  be  some  moisture  condition  in  a 
soil  which  is  best  for  the  development  of  the  plants,  of- 
ten termed  the  optimum  content. 
i 

The  total  range  of  available  moisture  does  not 
of  course  represent  this  condition.   In  practice  the  mois- 
ture content  will  fluctuate  considerably,  forty  to  sixty 
percent  of  the  pore  space  being  considered  essential  for 
best  growing  conditions.   It  should  be  the  object  of  every 
irrigator  to  apply  just  such  an  amount  of  water  to  his 
land  as  to  bring  the  water  moisture  content  as  high  as 


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24 


possible  without  experiencing  deep  percolation  losses, 
and  at  such  periods  that  the  minimum  water  content  just 
before  irrigation  does  not  approach  the  wilting  coeffici- 
ent.  The  extent  to  which  this  is  achieved  in  practice  is 
illustrated  by  the  experiments  of  P.  R.  Adams  on  Sacramento 
Valley  Soils.   Fig.  IV  shows  the  percentages  of  soil  mois- 
ture in  a  fine  sandy  loam  soil  before  and  after  irrigation 
for  various  depths.   The  diagram  showsthat  the  moisture 
percentage  reached  or  closely  approached  the  wilting 
point  in  the  upper  three  feet  of  soil  before  each  irriga- 
tion, but  that  it  was  well  above  the  wilting  point  through- 
out the  season  in  the  third,  fourth  and  fifth  feet  below 
the  surface. 

The  results  of  a  considerable  number  of  experi- 
ments conducted  on  the  moisture  properties  of  soils  under 
field  conditions  of  irrigation  are  summarized  in  Table  V. 


3    i 


lo  aa 


/y  fj'9il 
- 


wol9cr  cfsol  rfctll'i 


3    1C 

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25 


TABLE  V 


Character  of  soil 

Usual  ave 

rage  percent 

of  total  moisture 

i 

At  wilt- 
ing point 

— 

i 

When  irriga- 
tion is  de- 
sirable 
—  \ 

After  irriga- 
tion when  free 
to  drain 

"" 

Sandy  soil 

,         | 
3    ^ 

, 
5 

8 

Sandy  loam 

5 

9 

13 

Pine  sandy  loam 

6    ^ 

12 

18 

Loam 

8 

14 

21 

Silt  loam 

10 

16 

22 

Light  clay  loam 

?   13 

17 

22 

Clay  loam 

14 

18 

22 

Heavy  clay  loam 

16 

19 

23 

Clay 

18 

20 

24 

It  is  evident  that,  even  after  a  heavy  irrigation,  the  aver- 

.  ;j* .  rr.ted  cenc^  ttcn,    the  fl^'-d 
age  percentage   of  water  held  in  a    soil   to  a    depth  of  ten 

feet  is  far  below  the  maximum  capillary  water  content.   In- 
variably only  the  top  foot  or  often  the  top  layer  contains 
that  quantity.   With  increasing  depth,  there  is  invariably 
a  decrease  in  moisture  content  until  about  eight  to  fifteen 
feet,  it  is  very  little  above  the  point  of  slow  capillary 


52 


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26 


TABLE  VI 

Table   showing;  the   distribution  of  moisture   after  irrigation 

(Widtsoe) 


Depth 

Depth 

of  Water 

Applied 

In  the  Spring 

7.5  inches 

5  inches 

• 

2.5  inches 

1 

25.80    ' 

' 

- 
23.56 

18.57 

18.42 

2 

21.88 

20.73 

13.81 

17.49 

3 

20.17 

i 

19.09 

13.53 

15.65 

4 

17.72 

17.84 

13.46 

14.07 

5 

15.91 

16.29 

12.32 

13.98 

6 

14.55 

15.83 

11.81 

13.14 

7 

14.21 

15.60 

12.31 

13.26 

8 

14.15 

14.81 

12.70 

12.93 

Dr.  Widtsoe  has  termed  the  percentage  of  moisture  held  in 
field  soils  to  a  depth  of  eight  to  ten  feet,  with  the  top 
foot  in  a  saturated  condition,  the  field  water  capacity  of 
a  soil.   In  general  it  has  been  found  that  it  does  not 
vary  very  much  from  the  optimum  water  content  for  plant 
growth.   For  various  soils  Dr.  Widtsoe  gives  the  following 
values. 


iv 


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27 


Soil  to  a  depth 
of  8  feet 

Field  water  capacity 
expressed  as  a  per- 
cent by  weight 

i  — 

'Registered  moisture 
'percent  by  w  eight  on 
'the  basis  of  forty 
'to  sixty  percent 
'moisture  content  and 

'thirty  percent  pore 

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28 


CHAPTER  III 

THE  CLIMATE 

The  first  factor,  influencing  the  net  Duty  of 
water,  that  will  be  considered  is  the  Climate  under  which 
irrigation  takes  place. 

The  annual  precipitation  and  its  seasonal  dis- 
tribution, together  with  the  temperature,  humidity  and 
wind  movements,  have  a  very  marked  and  evident  effect  up- 
on the  amount  of  water  required  for  crop  product! on, length 
of  irrigation  season  and  the  number  of  irrigations  that 
are  applied. 

The  climate  .affects  not  only  the  total  seasonal 
duty  but  is  also  mainly  instrumental  in  determining  the 
actual  monthly  distribution  of  the  water  requirement- -a 
most  vital  factor  to  be  considered  in  the  design  of  the 
distribution  system.   The  monthly  requirements  are  con- 
trolled by  the  crops  grown  and  the  locality  under  consider- 
ation.  Alfalfa  or  pasture  in  any  arid  region  usually  re- 

'.$:r  *.tfcc:          .  gg  -  -:-'* 
quires  water  throughout  the  growing  season,  or  from  early 

spring  until  late  autumn,  while  a  grain  crop  requires  water 
during  not  more  than  the  first  half  or  two- thirds  of  the 
season.   Potatoes  require  water  throughout  the  season,  but 


Ill  H221AHO 


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oJsfltlXO   add1'  aJ.  bsisbienoo  0d  ^ 


lb  lanoaaDe   ad-x  ba,-   nolt.d-iqiog-ic    Lsaaaa 

bns  ^d-iJbitrujii   «  sijjctaioqnis^   sdd-  .Ictivr   nsddsaoJ-    ,nold-ucfJtid 


£)C--iq  qcio  'icl  bs-iiupsi  'isd-.aw  lo   dm;o::u3   sd,  "no 
J-3iId-   aaol-J33iirix   Io   -iscifta/n  sricr  bna  aoasaa   nolJagjrcii  lo 

..bellqqa 

edi  ^X«o    tort  ilool'l'-i 
nx  Ijed-rriiiiui 
3d-3Tr  sxl.t   Io 

srio    lo   iigiasb   sr{j  nx  bs-isblenoo   ad  o?-  10  Jo/si 
-noo   91  '•  acfneKisrriifpa'i  Ylr£d-noa\  aixiT      .fn&d-e^e  noict'JJcf 
TC3i)ianoo  i?baw  -^liapcl    sxld  bus  nvfo'i^  aqoio   sii^  ^'cf  ball 
-91  vLL&u&u  noxriai  blifi  ^os  ai  arrwaaq  10  s'lIfillA      .aoiJa 
10    .noasaa  30  .twig  84*  ^wodsiioi'rid-  tsd-atf  aaiinp 

qoio  nxs^a  «  eliriw   tajKOd-i/a  si^X  XiJ-ru;  gnx 
id  Io   Bbnixld-owd-  10  'iXs£i  ;teixl  »ifi  itda'u    siost  droc  ytlii/b 

.~t-:- 


29 


do  not  need  it  so  early  as  grains.   Orchards  on  the  other 
hand  when  well  cultivated  need  little  water  in  the  early 
summer,  the  greater  part  of  their  requirement  occuring  dur- 
ing the  latter  part  of  summer  and  early  autumn. 

The  following  two  Tables,  taken  from  the  report 
of  Don.  H.  Bark  are  typical  of  the  irrigated  sections  of 

Idaho.   The  crops  and  soils  were  divided  into  two  classes 
1911  '  18  ' .     ' .  325  ' .  52  *  ' .  ZO?  .  945  ' .  750  ".  199  ' .'     '  r.  .  7€3 

(1)  Grain  on  medium  clay  and  sandy  loam, 

(la)  Alfalfa  grain  on  medium  clay  and  sandy 
loam. 

(2)  Grain  on  porous  sand  and  gravelly  soil, 

(2a)  Alfalfa  and  clover  on  porous  sand  and 
gravelly  soil. 

TABLE  VII 

Summary  of  Depths  of  Water  Applied  by  Months  to  122  Fields 
of  Grain  on  medium  clay  and  sandy  soils  f/zj 


Season 

~T~ 

No.  of  'April 
plots  '15-30 

r~  ~  i— 

May  'June 
i 

i 

~r~ 
JulyjAug. 
i 

t 

Sep.  'Sep. 

1-15  '15-30 
i 

1 

'Total 
'for 
'season 

'feet 

feet  'feet 

feet  'feet 

feet  'feet 

'feet 

1910 

39    '    .00 

i 
.320  '.645 

T 

.495  '.095 
i 

i 

.00  '.00 
1 

i  ~ 

'1.556 
i 

1911 

49    '    .00 
i 

.021  '.717 
i 

.428  '.006 
i 

.00  '.00 
1 

'1.172 
i 

1912 

34     '    .00 
i 

.000  '.914 
i 

.650  '.059 

.00  '.00 
1 

'1.623 
i 

Average 

:•            '    .00 
i  "           t 

.114  '  .  759 
i 

.  524  '  .  053 
t 

.00  '.00 
1 

'1.450 
i 

Percen- 
tage of 
Total 

i             lit 
I             i              it 

1             '    .00'  "7.86  '.52.34  ' 

i 

i 

36.14  '3.06 

1 
1 

.00  '.00 

i 

'100.00 

adi  no   abiarionO      .anlaig     a£  ^Iies  oa   11  b,99n  Ion  ob 
9&  nl  -tecfaw  sl^ll  baa«  ba^viciluo   llsw  naiiw 


lo  cf'isq  tenets  I 


lo   anol^osa  fisiaaiiii   sri*   lc   Ijsolqipt   sic   ah*a    .H    .noQ  lo 
pw*  -oinl  bstivlb  srcsw  alloa  ana  aqoio    ^11'      .oriebl 
,mQoJ  -^fcrtaa  bn«   ^B!O  ns/ibam  no  alBiO   (1) 
bnc   ^alo  nu/lbom  MO  'nisi^  ells'UA    (si) 


,1103  ^ilsv.313  bn.3  bGJBa   eiro-ioq  xio  nis-iS 


bn«a  auo-'tcc   no  isvclo   baa   BlXallA 

.  i  ioa 


,  J.3AT, 


.T1     .qaa'  .q92'  .guA1  ^Itfl/  sitt/L'-S*^1  Xif;      [ 

"  '  r^F  "^  r'  -  r    r ' 

i  i 


1 
1 


-     _^-^_        --    -   T,       - 

jrf.  V     i_!^_  -'S  ^-fej-iE  "^ ;  T^ 

oo. 'oo.  'eeo.'aeK'a^e.'oesJ   oo.      es 


00. '00.    '  300.' 8S£.' V..7  .' 

' 


'  '.'       0  .         6£ 


n 

J  . 

' 


'00.    '  •      °°- 

!  »  I  '  ' 


i 


it 


I  I 


I  •  I  '  «  -.:»  ! 


30 


TABLE  VIII 

Summary  of  Depths  of  Water  Applied  by  Months  to  46  Fields 
&f  Alfalfa  on  Medium  Clay  and  Sandy  Loam/fr?; 


Sea- 
son 

No. 
of 
plxts 

April 
1-15 

April 
16-50 

May 
l. 

June 

July 

Aug. 

Sep. 
1-15 

Sep. 
16-30 

Total 

1910 

17 

.055 

,018 

.531 

.720 

.002 

.551 

.004 

r 
.000 

2.54 

1911 

18 

.00 

.025 

.  525 

.308 

.945 

.750 

.199 

.051 

2.78 

1912 

11 

.00 

.000 

.508 

.445 

.697 

.474 

.038 

_ 
.000 

2.10 

Aver- 
age 

r« 

«3       .t 
.018 

! 
.014 

.521 

.490 

.748 

.592 

.100 

.010 

• 

2.50 

Per- 

. 

1 

cen- 
tage 
of 
To- 
tal 

f~  '  '•* 
f 

.72 

: 
.56 

, 
20.90 

29.05 

, 
30.00 

25.75 

4.02 

.40 

100. 

Irrigation  water  is  usually  applied  during  that 
part  of  the  year  which  corresponds  in  general  with  the 
period  of  plant  growth.   The  time  to  start  irrigation  is 
largely  dependent  on  the  initial  amount  of  moisture  present 
in  the  soil — due  either  to  winter  rainfall  or  fall  irriga- 
tion, the  available  water  supply  and  the  crops  to  be  grown. 
Soils  which  have  a  good  water  retentive  power  and  which  have 
been  subjected  to  either  fall  irrigation  or  winter  precipi- 


OS 


HIV 


^gA 


£ 


.  •-. 


S8V.S 
001.2 

Oo.2 


00.001 


—  1 

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—  I—       "I 

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1 

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,_.            II..-—,.* 

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CSV.'  ise. 

l~            i 

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ria«    I  3AO 
UG  i  •     o  4r  -  « 

80S.1  S23. 

320.'       00. 

81 

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&Y£    !V8d. 

S^  .  '  803  . 

000.'       00. 

II 

2191 

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>i  . 

263    '  8£V   ( 

rQ6£.  !  xsg. 

MO.1    SIO. 

63J3 

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lo 

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5V.S21  OC.X 

30.6E'  09.02 

•z-r-            QV 

C?O     .                                 -i     *        • 

I3-T 

t 

i 

1 

el 


nellqqB   -^llB0afJ  el  -is^sw  noi*?^±fxl 
jijr«   is-isnss  nl   sbno^si-xoo   doldw  "iss^  ed^  lo 
d-xad-a  o^   atnld-   siff      .d^wbig  .tnelq  lo 
le  *lu»ttB  l*lilai  9d^  no  tfnebnsqeb  vli 
to  Ilalrc-Ui  tsctni*  od-  ^xedtls  ewfc—  II 
aqoio   arl^  bn/;  ^iqqtie  I9v^«w   sldsllave   3i'ct_  «r 
svsrl  ilolriw  fcna  lowoq  9vJ:d'n9d'»rr  ri  :  -s   ovsti  i.- 


-Iqioeiq 


o  I  bs: 


51 


tation,  will  generally  be  found  to  have  sufficient  initial 
water  in  the  soil  to  start  plant  growth.   This  is  due  to 
the  fact,  as  already  shown,  tiiat  the  water  may  be  stored  in 
soils  to  a  considerable  depth  as  a  film  surrounding  the 
soil  particles.   At  Utah,  where  most  of  the  precipitation 
comes  in  winter,  it  was  found  that  in  the  spring  most  of  the 
water  that  fell  during  the  preceding  winter  was  held  in  the 
upper  eight  feet  (See  Table  VI).   The  quantity  held  in  the 
soil  varied  with  the  percentage  of  water  in  the  soil  in  the 
autumn.   If  the  soil  went  into  the  winter  in  a  dry  condition, 
practically  all  of  the  winter  precipitation  was  found  in  the 
spring  in  the  upper  eight  feet.   If,  on  the  other  hand,  the 
soil  was  well  filled  with  water  in  the  fall,  a  relatively 
small  quantity  of  the  winter  precipitation w  as  found  in  the 
upper  eight  feet  of  soil.   The  upper  couple  of  feet  were,  in 
both  instances,  fully  saturated,  and  the  percentage  dimin- 
ished steadily  with  increasing  depth.  Hence  it  is  clear 

that  when  the  soil  was  fairly  completely  saturated  in  the 

iur    r'-i--;    :;c<    c-iuy  evepoi^.-te  tc^.r-r.  Iiave  fcii<j 

fall,  the  winter  precipitation  passed  down  beyond  the  eight 
feet  limit  or  the  root  depth.   Prom  1902  to  1907  the  per- 
centage of  winter  precipitation  found  stored  in  the  soils  in 
the  spring--the  soil  going  into  the  winter  in  a  dry  condition 
--varied  from  sixty- three  to  ninety-eight  percent.   It  is 


wi       fl         *iB*a  o*  lioa   9:tt  n     is 


nif>^o^'3  ntin  a  SB  d*qeb  elda-isbianoo   B  o^  alloa 

lioa 


o  iaom  ^oliqa  srtt  n±  ^aiflt  on.'o'i  asw  *1    .leiniw  ni   ao:noo 
*  ni  bled  BBW  i^nlw  rjflJtbaow  artf  'anlnuB  liai  *«U 


B   fll  folea  ^i^xrp  aid!      .tJV  eld-T   9  " 

Iloa 


a  s^  cl 

tb   a  nl  ts^iw   sdi   o^al  *naw  iioa   3rl:  . 

ni  tool  aawnoldc^lQioa-sq  «*nl»   ail*  lo    Ila 
i£t    ,6flad  -xarfio   aitt  no    . 

evitEis-r   s   ,ifi       i      ai  '  ''  Jioa 

-  w 


Ilsma 

ni   .a«w  isello   alq«oo  la^qw  oifl1      .lioa  lu   Joal  *rfsl» 

(     -      ao    tb9*is-«rt«E  Tfllwl   .asonactanl 


HOB 


SCSI  ^o^    ..ri*qab  *ooi  a*W  10   *l^ 

lo 


.ii«v-- 


32 


evident  therefore  that  in  districts  where  the  precipitation 

comes  in  winter,  early  spring  irrigation  may  have  but  lit- 

ijRer  -  ••!       11  b«lo«"  th'it  vh-leh 

tie  value.   On  the  other  hand,  where  the  winters  are  dry  and 

the  summers  wet,  early  spring  irrigation  should  prove  very 
profitable. 

Porous,  coarse,  sandy  or  gravelly  soils,  which 
have  but  little  retentive  power,  will  require  early  irriga- 
tion and  for  new  crops  may  even  require  irrigation  before 
planting. 

The  effect  that  the  rainfall,  which  falls  during 
plant  growth,  will  have  depends  largely  on  the  amount  of 
precipitation  and  the  relative  humidity  of  the  district.  It 
has  for  instance  been  shown  in  Idaho,  "that  a  light  summer 
rainfall  has  but  very  little  influence  on  the  IXity  of  water, 
most  of  it  being  evaporated.   Heavy  rains  of  .5  of  an  inch 
or  more  at  a  time  seem  to  have  beneficial  effects,  but  the 
Idaho  atmosphere  during  summer  is  so  dry  and  the  soil  is  so 
warm  that  lighter  rains  than  this  seem  to  do  more  harm  than 
good,  for  they  not  only  evaporate  before  they  have  had  time 
to  penetrate  into  the  root  zone,  but  effectually  destroy 
any  soil  mulch  that  may  have  been  formed  by  cultivation." 

The  beginning  of  the  irrigation  season,  may  in 
some  cases,  also  be  considerably  affected  by  the  temperature 


•iq  axicfr  s^eiiw  atfoistfaJLb  al  tfsrict  a-xclaiarld-  ctaa£>iv9 
_4  •  vsm  ridds^-Liii  s^-toq2  Y-t**39    tistfniw  ni  asntoo 

)  sis    Bi9d:ni?F  slid-   aigrlw    tbriB£{  -isd^o   arid-  rtO      .at/lev   eld 
fclcorle  aoltfaglfi.t   gnliqa  Y-^^39    t*91*   ai^rnmwa  srfct 

.  Dieted-  llptq- 

iiw   «allo8   Y-t-t9^'3*1?  ^o  Y^11-32   *93iJ3oo    tS^oioi 

9''lil/pS1    iliW     (TQ'flDQ     OVl  +113^91    SlC^li     *Od    SVBii 

0i'V9  ijsm  aqorio   wan  io'i   bne  noid1 


ellsl  riolrfw    tllalrilai  d-oaTls   exH 

lo    jiOJOffiB   9ilJ  no   ^is^tol   35n.9q9r)   sVBrl  II  iw    ,£f*v70'i3 
sii)    ail*  lo  v^ifjlmwri  9vioBlsi   9/Id1  bnw  n 
-xlgil   -3   •tsrW"    .c/JcpI  ni  rr,'/o;la   naod  gonB^a^x   10! 

1'lni   slJail    iri6V.  ;t0d  SBX! 

lo  3.  lo  snlai  TjvsaH  .bata'toqeva  ^niad  J±  lo  cfaom 
,8^05119  leioi'isnscf  ev/3i{  od-  ntsaa  amlo  :s  *s  s'torrt  to 
oa  ai  Xlou  sj^ct  one  *^i6  oa  si  narwyja  gnliub  sisi 
jiailct  rtwaxl  aiom  ob  od-  msps  sirfd-  nsiid"  aalBi  isd-d^II  tarid-  .i 


,  anos   -tool   arfd"   otnl   sd'BTd'snoq  cd1 


nJE  Yfi!n   -. 

add;  ila  vi       .         i  .00   dd  CS!B    .  2981-0  «cioa 


of  the  water.  Cold  water,  if  applied  in  large  quantities, 
will  lower  the  temperature  of  the  soil  below  that  which  is 
best  for  plant  growth.  Hence  if  the  soil  has  sufficient 

water  for  plants  to  thrive  on,  it  will  be  detrimental  for 

the  <U?fcMbut,!  JT 

plant  growth  to  apply  irrigation  water cf  a  temperature  be- 
low that  of  the  optimum  soil  temperature. 


id  fit  fcallqqfl  11   ti9^s?/  bloO      . 
wolstf  Ilos   sxid-  lo  »txtffii9.q-rra^   a 


.j  .  -to' 


d    Cliw  *1    «no  evhxrtt  o* 


;ae-i   I±oe  ntwmi^qo   eel*  lo   ct^tid   wol 


34 


CHAPTER  IV 

MOISTURE  DISTRIBUTION  IH  THE  SOIL 
mea;;j) 

It  will  be  well,  before  discussing  the  question 

of  the  distribution  of  the  moisture  throughout  the  soil, 
to  take  up  the  question  of  moisture  movement. 

The  moisture  in  the  soil  is  subjected  to  various 
forces  of  which  the  following  are  the  most  active. 

(1)  Gravity G. 

(2)  Capillarity C. 

(5)  Film  Forces,  such  as 
molecular  attraction, 
surface  tension,  etc...F. 

In  an  air  dried  soil  there  is  a  condition  of 
equilibrium.   The  moisture  contai ned  has  distributed  itself 
according  to  the  forces  acting  on  it,  in  this  case  being 
primarily  film  forces.   If  the  hygroscopicity  of  the  soil 
is  satisfied,  the  moisture  acting  under  capillarity  and 
film  forces  will  distribute  itself  uniformly  throughout 
the  mass.   If  now  this  state  of  equilibrium  is  disturbed, 
as  by  the  addition  of  water  or  by  evaporation  from  the  top 
soil,  the  soil  moisture  will  tend  to  redistribute  itself  to 
the  new  conditions — bringing  about  thereby  a  movement  in 
the  soil  moisture.    iv.oisture  will  always  move  from  the 
wetter  to  the  drier  soil  or  from  the  thicker  to  the  thinner 


VI   /IS 

aar  *r 


arid1  gnlaauoalb   atolscf   ^II?w  9d 
\Iioa   9itf  d-wodawo-tt**   ai^eioni  arid-  lo  nojt*i/dln;tell>   9& 

.ctnQfr.evont  sti/cteioiTE  lo  noiJaawp   3:Irf   qw  ajiad-  ocr 
awoii.sv  oc^  bsctostcfwa  ai   Itoa    9/a   nJ   sii/ctaloa  siff 

J-aonx  erict   si-a   :^i-.7ollci   oai  39010! 

...........  .-tfsv^.  , 

iqai)    . 

''i   ;$) 
loRt 

lo   rtci.Uiiuoo   3'ai-   aiedJ-   I  toa   bsJtib   lis   K/S  nl 
i  bactwdlid-alfi   ajarf  -ban  -tetnoo   siwj-aloir,  . 

gnclea'  32^0   si---  ..-ti  no   yild-os  aeofio'l      ild1   oct  ^a 

I  to  a   «W  lo   -£cJio±qooaot^.  -I      .aso^icl  mill  ^ 

bus  ^1'iBlIlcflo  -isbnjj    yiictos   s^urfal-cm  .3±lcitae   al 

j  ^imtoliru/  'ilaacM  scfLrcJi^alD  II  iv    as  one 
al  fauJncflilupe  lo  ets.ia   sixi*  won  II      .aaflia  srict 
qocr    3:1*  rno'il  nold-s'xoqs-vo  .'  ^cf  ic  is-isw  lo  noid-lfs&B   srict   ^d  aa 
o*  llee*!  stfxfdiTKtelbet  o*  bngi   Ii±v/  snu^alqia  Iloa  sxl:    «J 
ni  ^nsmsvom  B  ^daiaiit   *uods  golsai^jd-^anoi^lbrtoo   wan  arid 
arid-  moil  9vom  a^awls  lilw  e-u--  .  3i.udelo«.  lioe   orii 

iioa  isi^b  srii  cct 


35, 


film — the  affinity  between  soil  particle  and  moisture  be- 
ing so  much  greater  in  the  latter  case.   And  once  contact 
by  this  means  has  been  established,  it  is  surface  tension 

that  drags  or  pulls  the  other  particles  along. 

the  lento 

If  the  moisture  content  is  somewhere  near /capil- 
lary point,  the  movement  and  the  distribution  will  be 
primarily  due  to  P,G  and  C.   When  the  maximum  retaining 
capacity  of  the  soil  has  been  reached  any  further  addition 
of  moisture  simply  slides  off  the  already  present  moisture 
film, --neither  capillarity  nor  film  action  having  any  hold 
on  the  water,  gravity  alone  acting. 

The  lateral  movement  of  moisture  is  dependent 
not  so  much  on  the  result  of  capillarity,  film  action  and 
gravity,  but  to  a  greater  extent  on  the  first  two  only.  The 
result,  as  will  naturally  follow,  is  less  than  in  the  case 
of  downward  movement.   Gravity  will  rather  tend  to  spread 
the  laterally  moving  water  downward  in  a  fan- like  formation, 
giving  thus  a  uniform  distribution  only  below  the  topmost 
surface. 

The  upward  movement  of  the  moisture  is  entirely 
identical  to  the  downward  movement,  except  that  in  this 
case  the  action  is  a pains t  gravity,  whilst  in  the  former 
case  it  is  aided  by  gravity.   As  the  particles  in  the  top 


-ed   a         .  '.onx  bns   sloWiaq  HOB   neswdsd  -tflnttla  ad*—  Mil 
*3s*nco      90no  bnA      .sacs  <i9**i5l   erf*  ai  1,8*39*13  do0m  oe 
nolaflg*  doalioa   ai   *i    <£»d3ild**39  n&dd  Siiit   au^sm  aid* 
•  anolfi  aslold'i.'sq  I8d*o  04*   ailwq  10    agenl)   * 

;:G2   ..."    ctuecfiicc   st?/*aiont  ad*  II 

ad  lliw  ^oi.t'^J•cfl^d•ei5  srl^  bne   ^ns-Ttavom  9J±f    tctnioq 
.-i  jnuKJtXJMi  srl*  nedW      .0  &ns  0,/9  ocT   girb  ^Ili 

-iul  ^rifl  fo9Jlo--9i  naacf  sBxi  I  JOB   eifct  lo 

aiOM  ctnsastq  ^se'xijs  sd^  Tio   aafilie  ijlqat  JE   e^ujaioa:  lo 
ii  noi-ioa  nilJl  ion  •&tialLtq*o  lariJlen--.  .mill 
.^nicfOB  enol3  ^ctivaig   «ts*aw  9d*  no 
cfnsbns'-jsfi  ax   9rin*slom  lo  Jxisir.svom  Isisctal   9ifT 
£>ns   nol*3fl  mill    tTC*liBlIlqoo   lc   lluaai   sri*   no  rfowni  oa  . 

ovtf    *aill  9dJ  no  tfcelxs  leJseia  B  ocf  ^0cj 
9330   an*  ni   nsrl*    aasi   al    .woilol  ^IlJB*w;*sn  illw   ae 

ct  5ns*  1911*31   lllv?   iptlvfiiO      .*n9fn9vom  b^awrrwof)    lo 
a.  nl  6iJ8.wn-*o&  -i3*Bw  ^nivom  ^Hai9*fll  sri* 

*r  *•* 

s  ami* 


9d*  lo 
*q93xs    ,  "-^  o*.  1^: 

j  '  '  r\f\ 


qo* 


36 


surface  dry  out  as  by  evaporation,  there  will  be  a  gradual 
readjustment  of  the  moisture  particles  from  the  thicker  to 
the  thinner  films.   But  as  evaporation  is  a  continuous  action, 
so  too  will  be  the  movement  of  the  soil  moisture  from  the 
bottom  towards  the  top,  until  the  loss  of  moisture  will  be 
felt  throughout  the  entire  soil  mass. 

The  problem  that  the  irrigation  engineer  faces, 
is  to  be  able  to  tell  to  what  extent  this  moisture  movement 
will  take  place  in  various  types  of  soil  or  what  the  dis- 
tribution through  the  mass  will  be.   It  is  essential  for  him 
to  know  these  matters,  since  whilst  for  one  type  of  soil  the 
water  applied  will  wet  the  mass  throughout  the  root  zone,  on 
another  soil  the  larger  portion  may  be  lost  by  deep  percola- 
tion, the  film  action  and  capillarity  being  too  small  to 
store  the  water.   It  is  evident  that  the  degree  of  success 
which  the  individual  irrigator  attains  is  directly  propor- 
tional to  his  ability  to  grow  satisfactory  crops  by  using 
reasonable  quantities  of  water. 

Irrigation  water  which  passes  below  the  root  zone 
of  ordinary  crops  carries  with  it  in  solution  valuable  plant 
foods,  thus  tending  to  ultimately  render  the  soil  infertile, 
or,  as  often  happens,  if  the  downward  leaching  is  checked  by 
an  impervious  strata,  a  water-logged  condition  results,  fa- 


^  as 

slo.ti  artf  lo 
airojjnltfnoo   ^   si  nold-B*ioqBve>   se  JxrtJ      .  sell. 

ia  Ixo3    wi*   lo  ^nsmavonv  srl^   acf  11  iw   oo^  oa 
m  lo   saol   eii?   Ii*ra;   ,qc;       M  sbie 
Ki  Jloa 


aewtdvom  yxi-.^sJtoKt  eliJ   ^rrsJxo   ^aw  o*  ilai   ot    glda 
.-a±fi   an'*  -td.'iw   rcc   iio^    10   asqtf   awoliBV  nl    ao^lq   ails*   Iliw 
loi  lal^neaaa  el  *I      -ad  illw   aaam  Siio    il. 
llos   Ic    aa^i   SKO  -io'i   *BllrIw  sorrla    ,.ai9J*cir.  9aa/id-.  woroi 

srtt   ctaw  111* 


no 

-alooisq  qesfo 

od-  IIr;r.2   oo-t   ^nlod  •^•ta'-J^-ta^80  ^i-a  uoWoa  ;rJ11  exit   « 
aasooua    lo   aeigeb  ari"  *.^#  tftwfilva   el  *I      .is*«w  *d* 

rfolrlw 


-loqoiq  \; 

%d  aqoi 

.•'ie-Js-,v  lo   asid"! 

tfooi  srid  wof&d  aaassq  riolri*  'xad'aw  aoljss^^1 
eirfaxilBv  noljftloa  nJL  *I.  tfTJtir  a^insaf  eqoto  Y^^-^O  ^ 
Iloa  aiit  isbori  ^Is?=m±«y  °*  Sftlfcna?  eurij    .abool 


i  a         ifi»?/ob  sxl^  IT  ,an3:,q-a  a 


37 


v curing  the  rapid  accumulation  of  alkali  and  hastening, 
to  a  marked  degree,  the  non- productiveness  of  the  soil, 
and  thereby  the  failure  of  the  irrigator.   Consequently 
the  importance  of  gathering  information  concerning  the 
depth  to  which  soils  may  be  wetted  by  irrigation  cannot  be 
overestimated. 

The  extent  to  which  moisture  will  distribute  it- 
self after  irrigation  is  dependent  on  the  frictional  resis- 
tance which  the  water  has  to  overcome.   As  soon  as  the 
frictional  resistance  of  the  soil  particles  to  the  moisture 
becomes  greater  than  the  forces  bringing  about  the  moisture 
movement,  the  distribution  will  decrease  rapidly  and  further 
penetration  into  the  soil  stopped.   The  cause  of  the  fric- 
tional resistance  becoming  greater  than  the  movement  forces, 
must  be  sought  in  the  theory  that  the  water  is  gradually 
used  up  in  the  form  of  films  in  its  downward  mavement.   The 
finer  the  texture  of  the  soil,  the  greater  will  be  the  ag- 
gregate surface  exposed  by  the  soil  particles  and  the  great- 
er therefore  will b e  the  moisture  distribution.   If,  there- 
fore, a  definite  quantity  of  water  is  applied,  it  will  be 
used  up  to  a  much  larger  extent  in  the  topmost  layers  by  the 
finer  grained  soils.   A  point  will  hence  be  reached  where 
there  is  no  longer  a  sufficient  supply  of  moisture  to  satis- 


lo 

aaanovld-oubc'iq-non  arid-  .  seigab  beiiiBia  B  o* 
ettf  lo  anuila'l  erf*  YCferi»*»  boa 
nl  ^ol'iarWas  1»  eonarfioqml  eri* 

sd   Jo/£n«o  noW«slitl  YOr  §0j**o-ff  &d  ^aia  ailoa  do  Id* 

atire  sis  vo 


Jilw 
laaoiJoJ-tl  eiW  no 

as  nooa   aA      .anwo-isvo  oJ  z#d  is*e  - 


saonol  arid"  na.x«  i^«9'ts  estnooad 
.CIlw  ncWxnJi^eib  srict    t*nainavom 
a3iiv.o   srfT  qqcte    Iloa   arf^   otfr.l   RClcTa 

,aamel  Jnsrr.&voir.  .^itt   r<  'tS    isctsaia  yilir.ooed  '  aon^aiaai 

XlI*J^>fii-=   ai  10*8*   sdcf  c^iit   vio*^    9xid   fl-t'^uca   sd 
eriT      .In&rwv-on;  IwuwnwoS  all  rtl  amlil  lo  mTO 

-38   9rfJ  ad   'iJtw  laJaaia  sri^   «Iioe   srl^  'io   a««;*xe* 
-jB9'ig   srfci-  bna   eeio^'iaq  iica   ed?   ^d  basoqxs  90fl.l*swe 
-«0€OJ*   .11      .nol^dxiieib  a-x^alom  eri*  edlllw  ^cl^- 

.  ecr  iliw  *i    .beiiqqva  ai  iscfsw  lo  ^;i*jctswp  s^l 
eridr  ^<J  a^iavBl   ^oomqo*  .ari*  :st  *ne-lx&  i3S*tai  dou.r.  a 


-a  1*33  o-t  9iwJaJt0ffl--lo  ^Iqqws  ioelpniwe  B  issnoX  oa  si 


38 


fy  the  wants  of  film  action,  frictional  resistance  will 
increase  rapidly  and  the  distribution  of  the  moisture 
diminish  abruptly 

Table  IX  shows  the  result  of  a  laboratory  exper- 
iment on  sandy  loam.   In  a -glass  jar  some  one  and  one-half 
inches  in  diameter  a  celluloid  lining  was  tightly  placed. 
The  whole  was  filled  with  sandy  loam,  and  sufficient  water 
was  added  to  give  an  irrigation  equivalent  to  one  and  one- 
half  inches  of  water  in  depth.   The  jar  was  then  covered 
with  a  paper  to  prevent  evaporation.   At  the  end  of  a  week 
the  soil  column  was  taken  out  of  the  cylinder  and  unrolled. 
Samples  were  taken  at  the  various  depths  indicated,  oven 
dried,  and  the  amount  of  water  present  at  each  given  depth, 
calculated.   Table   IX  shows  the  results  obtained. 


ili*  Qonatfslas-'i  ii;noiJoi'il   <noWo;j  mill  lo  edtffiw  ectt 
sift  io  noJt*i><JJfettfaJti>  apd-  bna 


y    •to   ^-tjj'aeri  3il^    swede  XI 

forK  €>no   Oiito^   i^t    asaiiyfl   nl      .;naol   \fcxiaa  xio 
.baoelq  ^1*118^   asw  gninli    ololwlloo   a  istfa;nBib  nl 
ie*fl.w  ^nsioi'Il^a  bfl  o  ,mecl   u&rias  rf^Jtv  1)91111   a.sa  sloii1? 
-sno  an^   aao  oi   ^naiavlups  nci^e^/'nl  ns  svlg  o*  bsbc-s  a**w 
bsidvoo  nerid-   a  BY;        '.    oill1      ..laqai,  ai  oetfsw  lo   aarioci  Had 
>I56%'  3  'io  baa   srLt  cfA      .nclcffi'ioqava  *ndv»nq  o^   aaqsq  a  rid 
.&£•.[  I  cam/  bn-2  -'fsbiil       )       'rf  'io   iwo   nsjis^   asv;  nrrj/Ioo   lioa   arid 
xisvo    .bs-J-O-L-JuI   aitfcjsij   awoltuv   ad*  ^3   n 

cavig  not  jaeiv,  •i&*^\v  lo   jciaoaxa    arid   bne    t 


jli/aa--:  3-?oi£a  .XI     sicfB1:? 


39 


TABLE  IX 


Depth  from 
surface  in 
inches 

Percent  water 
present 

Hyg.  coef- 
ficient 

Net  capillary 
water 

_  h 

1 

14.35 

2.04 

12.31 

2 

12.97 

2.04 

10.93 

3 

14.13 

2.04 

12.09 

4 

13.63 

2.04 

11.59 

5    ^ 

15.03 

2.04 

14.99 

6 

13.22 

2.04 

11.18 

7 

11.88 

2.04 

9.84 

8     ^ 

/ 

9.04 

i 

2.04 

7.60 

The  results  show  a  very  uniform  moisture  dis- 
tribution in  the  part  of  the  curve  AB,  and  the  abrupt  de- 
cline of  penetration  after  the  point  b  has  been  passed. 
Similar  experiments  conducted  through  a  longer  period  show 
that  with  an  increase  in  time  the  moisture  distribution 
followed  roughly  in  the  way  indicated,  always  converging 
towards  the  point  c. 

These  conditions  are  not  necessarily  met  with  in 
field  practice,  the  part  be  of  the  curve  having  been  forced 
down  to  a  much  greater  depth  by  either  the  rainfall  or  ex- 


:  -Isoo    . 


-alib  9iwi 


i 

! 

;    tfoeeotq 

15. 

21          ! 

t 

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3T'J   •  .» 

3-3.  M 

se. 

01- 
i 

£0.3 

ve.2i 

eo. 

21 

!>0  .  2 

51.  M 

63. 

11 

J^C. 

53.  SI 

ok. 

£1 

. 

SO.  31 

81. 

11      ; 

*c  . 

t 

22.51 

MS. 

e 

: 

be          i 

88.11 
t 

Oc>. 

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K>.S    ; 

K>.€           ' 

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rale 

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ijj  ~<ri3V  -13  .woiJa 

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f>n.-i    ,9A 

3V100    a:Ii   lo 

diiq   9£ii   J 

sio'il 

.  :aa 


.p9aa-'c  n^ocf  a 
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cf  drJoq 


8 


cij'sri^s.rraq'  lo   snllo 


'  -Ji. 


cl  noacf 


JSrfT 

tt    -  oo.".  blsll 

ia  iloum  a   oct.  nwofc 


40 


cessive  irrigation.   But  it  is  abundantly  clear  that 
the  distribution  when  the  soil  is  in  an  air  dry  condition 
stops  at  a  very  marked  depth,  where  the  frictlonal  resis- 
tance becomes  greater  than  the  forces  tending  to  distribute 
the  moisture.   Greater  attention  should  be  paid  to   lighter 
irrigations  so  that  the  total  distribution  abod  may  be  kept 
within  the  root  zone,  rather  than  forcing  it  beyond  that 
depth  by  excessive  applications  of  irrigation  water- 

The  frictional  resistance  will   be   a  large  ex- 
tent be  dependent  upon  the  initial  amount  of  water  present. 
The  greater  this  amount,  the  smaller  will  be  the  frictional 
resistance  and  the  greater  will  be  the  downward  penetration, 
and  the  abrupt  change  in  moisture  distribution.   It  is  a 
matter  of  common  experience,  the  farmer  finding  that  the 
water  does  not  penetrate  the  soil  deeply  during  the  first 
year  of  irrigation;  but,  as  time  goes  on,  the  soil  becomes 
wetter  to  greater  depths,  and  at  the  same  time  less  water 
is  required  by  his  crops. 

The  moisture  content  of  the  native  undisturbed 
soil  in  arid  regions  is  usually  below  the  point  of  lento 
capillarity.  The  first  water  added  is  used  to  bring  the 
moisture  content  up  to  this  point,  and  as  this  is  accom- 
plished, water  moves  downward  freely;  the  plants  being  en- 
abled to  secure  their  water  supply  with  a  corresponding 


d-axfcf  isslo  ^Xcfiusbiurda  al  d-x  *«S      .noldflgxTix  sviaaso 
n.  '  ;  iis  ns  ni  al  Ixoa  said1  naifw  ncld-wo'lndexi) 


oJ   •gnibnsd'   asoiol   s.ril  ncrW   iscta©^   asmoosd 

feisq  scf  bluoiia   noii'nad-^a.  na^asiO      .aiwd-alom  srfj 

>  " 
qasi  ed  ^sr.T  f50;Jr  nol^udiiJtalJb  Iccto*  ari*  ctsrlcf  oa 

'  -dl   ^nicyicl  nsrid"  isr.utei   tenos   d~oo 

.19*3W  noits^irti  'io   anoijjeoliqqa  sviaasoxs  ^d-  rfcfqeo 
-x-3   e^tsl  &=..(.-t3v:  Lily  •  son  £3^.3  ia.3'i   Isnoi^olil   sriT 

lo   3-rtuoffw   Xeirfinl   arid-  noqu  dxittJbflsqsfo-iacf 
eor   Xiiw  nsllwiia   edt    ^nwo.TCS   elrf^ 
biejm/oi;   sri^   scf  iiiw  is^fiotg  erf.!   bna 

licfaib  .9^  r.'^  a  lorn  nl   o^riBrfo   iqmdB   9fi;t 

13)7^31   s-rlct    .eoriaiiaoxs  nommoo  lo 
.  Iqasb  lloa   srf^   sie'id'snaq  ^on  asob 

aemooscf  Ijoa   s^tt    ,no   eeos   smx*   aa    .  d-wd    joolctflgxTiJ:  lo 
aasl   emid-   ssise   sa'd   da  |j£Ej    taildqe5  TS^BSIS  °^  i 

.eqoio   aid 
wd-eifonw  svlcfsn  arid1  lo  drisdnoo  »«r  sriT 

%     NVsx 

ic   .tnioq    slid  woled  \LLstU3       iJ  &iiB  ni   lloa 

nlrtd     d  bsau  ai  fcsbbs  riT      .\^lrrslllqflo 

oo  com 


-ns  anls     adrtsq  s  .:i  isaw 

:aa 


41 


smaller  expenditure  of  energy.   At  the  Experimental  Farm 
at  Davis  the  results  obtained  are  given  in  Table  X. 

TABLE  X 


Depth 

T~        T 

1    .5'   1.5 
i      i 

2.5 

3.5 

4.51   5.5 

i      j 

Dry  at 

i      t 

i 

Percent 

vie:     i 

, 

Moisture  on 

1         ! 

i 

ovendried 

t         1 

O       |       tl 

basis 

|                  i 

1 

1  .     ^|  i 

(     i 

Boring   I 

'21.05  '18.16 

15.33 

17.04 

20.48*14.29 

6  ft. 

t 

i 

Boring  II 

'20.  49  !20.39 

19.06 

19.04 

23.19  '14.74 

5.9  ft. 

t      i 

i 

Boring  III 

'20.  55  '17.  92  '16.04 
i      i      i 

18.19  '13.26  '12.55 
i      i 

6.4  ft. 

fl*n9«Jtid«xa  sitt   *A      .Tranone  16 
.X  alcteT  ai  rtavlg  e-xa  fcanlacKfo 

X 


is  I  lama 


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1                                 *                     C~         t-    '  "~    *   ^ 

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0  '  6S.M1  8£.Q£ 

1 

:  4-O.VI'  S5.3I 

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1  frO.QI1  80.61 

es.os1  Gi>.o2!  ii    saiioa 

•  ^     1                   1      ~~ 

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;  29.  VI1  3-3.  OS1  III  sniioS 
i             i             ' 

41a 


These  results  were  obtained  under  typical  field  practice 

conditions,  the  samples  being  taken  in  an  orchard. 

sn   imiretti.ec!  dx;ty   of  th*  svsiiat.v  y. 

The  results  closely  follow  those  obtained  in  the 

laboratory.   Is  there  then  for  every  soil  a  definite  quan- 
tity of  water  which  will  distributees  moisture  uniformly 
throughout  the  soil  mass  to  just  a  sufficient  degree  and 
depth  to  prevent  any  deep  percolation  loss  and  be  of  maxi- 
mum use  to  the  plant?  It  is  still  too  early  in  these  in- 

v        various  soils-*   JbErrvs'.  <  :n£-  cl  tns  r^si*  :  te  »• 
vestigations,  which  are  being  carried  on  at  present,  to  ar- 
rive at  any  definite  conclusions.   One  fact  is  however  ap- 
parent, that  whilst  we  may  increase  the  duty  of  water  very 
considerably  from  purely  scientific  considerations,  it  is 
more  the  mechanical  application  of  the  water  in  field  prac- 
tice which  retards  the  obtaining  of  any  such  increased  ef- 
ficiency of  the  water.   The  tremendous  waste,  due  to  the 
improper  levelling  of  the  land,  the  loss  at  the  head  of  the 
border  or  check,  the  waste  at  the  end  of  that  border  or 
check,  the  skill  of  the  irrigator  and  so  many  other  mechan- 
ical factors  are  the  more  responsible  elements  for  the  low 
duty  realized.   Even  if  it  were  possible  to  apply  water 
in  such  quantities  as  would  be  befct  from  the  preceding  con- 
siderations, it  will  always  be  the  mechanical  factors  to 


90  '  -  -  •  cfc 


na       .J«&2J8 
98orfd-  woiiol  ^isaolo   aiiirasi 


-rump  gjtattob  a   Iloa  -fi 

e-wtfaxoai  alt  e^-dlid-aifi  IIlw  iloiiiw  i9*.ew  ic 

JnaloJtni;a  5  *awt   orf'aaaai 
o  9d  bru   aaol  nci^i-loo^^q   qssb 
oo  J   llita   si 


-qj  13V97/O.H  ai  ctoBl  anO      .acoieul-onco  **lnil9&   Tflcifl 


2"    dt    .  anolljsisblanoo   oJtlid-nsxoa   ~^i9iwq  moil 
-p3iq  Mail  nx  isdrsw  arid  lo   noldspiiqqa   laolrMffoe.         w   9'io 

r       «      r  *   -4- 

-lo  baaas-'iorii  iio«i    ^nc  lc  ^iiniad-do   and  aDiadoi  noxr.      QOXJ 

t__  •          1*V 

arid  lo  bagj   sxfd-  dB  o,cl   sdJ-    .finai   9rld  lo  aftlilaval  igqoiqwl 
ic  i9biod  dsdd  lo  bns  arid1  d;*'  adaaw  eifcf   »ioedp  10  i9b-i' 

:3Bt  o^   bn;a  lolu^i'til   sdd  Ic   XiJbls    ado    tii03iiO 

)JO;3l    i^JOl 


r,4«     aa   e.o«np 
•  rioi   ajnameig   9iai- 

I9*»w  \lqqa  od-   slcJiaaoq  9i9w  41*-  41 

-nco  3£ilc909ic   sdd  2101!  *«9d  8  SB  aoictldrisup  dp^a  ni 

^j-       n-to<*^   r'anir  .  ..iis.il  i'.T  dl   ^ 


42 


which  prime  attention  will  have  to  be  given  for  obtain- 
ing an  increased  duty  of  the  available  water  supply. 

The  California  Branch  of  Irrigation  Investiga- 
tions of  the  United  States  Department  of  Agriculture  has, 
in  co-operation  with  the  State  Engineering  Department  and 
the  Agricultural  Experimental  Station  at  Davis,  studied 
during  the  past  three  years  the  distribution  of  irrigation 
v/ater  in  various  soils.   Observations  of  the  results, 
which  may  be  regarded  as  those  of  typical  irrigated  soils, 
will  be  presented.   The  observations  were  made  under  two 
somewhat  distinct  conditions.   First,  .studies  were  made 
upon  various  farms  in  the  Sacramento  River  Valley,  on 
fields  producing  alfalfa  (lucerne).   Soil  types  represen- 
tative (according  to  the  Bureau  of  Soils  U.  S.  D.  A.)  of 
extensive  areas  in  the  valley,  were  chosen.   The  other 
conditions  are  those  at  the  University  Farm  at  Davis,  where 
alfalfa  was  grown  upon  one-fourth  acre  square  lots.   The 
surface  two  feet  of  soil  is  a  loam  of  remarkable  uniformity, 
and  the  third  to  eighth  foot  sections  consist  of  a  sandy 
loam  of  recent  origin,  pocketed  at  irregular  intervals  with 
coarse  sand  or  clay  loam.   This  fine  sandy  loam  lies  upon 
an  undulating  clay  which  extends  from  nine  feet  to  a  depth 
of  twenty  or  more  feet  below  the  surface. 


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43 


Sacramento  Valley  Experiments 

Silt  Loam  Soils.   In  Table  Xi  and  Figure  V  are 
presented  results  of  moisture  determinations  upon  three 
tracts,  classed  as  silt  loam  soils,  which  are  based  upon 
one  hundred  thirty-eight  six  feet  and  thirty- six  nine 
feet  borings.   The  curves  of  the  silt  loam  soils  converge 
gradually  from  the  surface  of  the  soil  downward.   This 
may  be  due  to  a  large  extent  to  the  fact  that  these  soils 
do  not  dry  out  as  rapidly  at  great  depths  as  to  the  more 
porous  sandy  loam  'soils.   The  average  amount  of  water  held 
after  irrigation  was  5.20  inches  per  foot,  or  enough  to 
fill  fifty- one  percent  of  the  pore  space. 


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45 


In  the  case  of  the  Bundy  tract,  four  irrigations 
were  given  of  17.22,  12.20,  11.55  and  7.77  acre  inches  per 
acre  respectively.  The  moisture  determinations  indicating 
that  the  following  amounts  were  retained  in  the  upper  six 


Irrigation  in  Acre 
inches  per  acre 

Percent  acre  inches 
per  acre  retained 
on  top  6  feet 

Percent  re- 
tained 

Percent 
lost 

17.22 

:;      4.01        i 

;  23 

77 

12.20 

3.27 

27    *;j 

73 

11.55 

4.05 

35 

65 

7.77 

4.73 

61 

39 

The  Table  shows  that  in  this  case  for  a  total  depth  of  nine 
feet  only  5.13  acre  inches  per  acre  was  retained  or  44.4 
percent  of  the  total,  55.6  percent  being  lost  beyond  the 
root  zone.   In  the  Hofhenke  tract,  the  following  additional 
results  were  obtained./^ 


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46 


Acre 
per 
tion 

inches  applied 
acre  per  irriga- 

r~ 

Acre  inches  per 
acre  retained  in 
the  upper  6  feet 

" 

Percent  re- 
tained 

r~ 

Percent 

lost 

18.76 

5.42 

29 

71 

15.74 

5.78 

24 
I 

76 

18.86 

5.36 

28 

72 

13.22 

3.50 

26 

74 

The  results  show  the  obvious  fact  that  the  quanta 
ties  applied  were  much  too  great,  the  losses  by  deep  perco- 
lation being  in  all  cases  excessive. 


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48 


Clay  Loam  Soils 

In  Table  XII  and  Figure  VI  are  given  the  quantities 
of  water  held  before  and  after  irrigation  on  a  number  of 
farms  having  typical  clay  loam  soils  as  determined  by  two 
hundred  ninety-six  six  feet  borings.   The  Figure  represents 
the  average  results.   The  increase  in  moisture  varies  from 
1.35  in  the  surface  to  .28  in  the  sixth  foot,  as  compared  to 
a  variation  of  1.15  to  .44  in  the  silt  loam  soils.   The  in- 
crease in  convergence  of  curves  with  depth  as  the  texture  of 
the  soil  increases  in  fineness  is  apparent.   The  water  con- 
tent decreases  appreciably  after  irrigation  with  the  depth 
of  the  soil.   It  is  therefore  doubtful  if  the  maximum  capil- 
lary capacities  of  these  soils  were  satisfied.   The  average 
amount  of  water  held  by  the  clay  loams  after  irrigation  was 
3.49  inches  per  foot  or  enough  to  fill  fifty-eight  percent 
of  the  pore  space  as  compared  to  fifty- one  percent  in  the 
case  of  the  silt  loam. 

The  following  additional  results  are  given  to 
this  type  of  soils. f/8) 


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j-ne  91  &q  sno  --r  j'l  i" 


49 


Farm  'I 
's 

;s 

rrigation  in 
.ere  inches 
er  acre 

Acre  inches  per 
acre  retained 
in  top  6  feet 

Percent 
retained 

Percent  Lost 

O'Hair 

6.24 

pr                  ^"i 

5.58      ,, 

j 

r,  57.   *„ 

45 

IT   5.18 

2.11 

66. 

54 

.:  mount 

5.24 

2.14 

66. 

54 

Guile 

7.28 

4.05 

<c  55. 

45 

5.94 

• 

5.41 

91. 

\ 

9 

Geer 

24.00 

•t    5.59 

25. 

77 

,.   18.19 

c    5.28 

18. 

82 

12.15 

5.57 

-+  44. 

56 

pa|- 

24.54 

h 

5.76 

„   15. 

85 

A  striking  condition  was  obtained  in  the  case 
of  the  O'Hair  field  in  that,  while  the  percentage  of  the 
irrigation  water  applied  retained  in  the  soil  decreased 
with  the  depth,  the  amount  of  moisture  in  the  soil  before 
irrigations  actually  increased  with  the  depth,  apparently 
due  to  the  capillary  use  of  ground  water,  which  stood  seven 
to  nine  feet  below  the  surface. 

In  the  case  of  the  Guile  field,  very  little  water 
penetrated  below  the  sixth  foot.  At  the  time  of  the  first 
cutting  the  moisture  content  of  the  soii  was  so  low,  that 


1 


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50 


nowhere  In  the  upper  six  feet  was  it  much,  if  any,  above 

c ;:^ :"      >  £ 

the  wilting  point.   The  same  conditions  were  approximated 
at  subsequent  irrigations.   This  no  doubt  accounts  for 
the  large  percentage  retained,  showing  again  the  influence 
of  the  initial  amount  of  water  present.   The  smaller  the 
amount  of  initial  moisture  present  the  greater  will  be  the 
amount  retained  and  kept  uniformly  distributed.   On  the 
other  hand  the  greater  the  amount  of  initial  moisture  pres- 
ent the  greater  will  be  the  downward  penetration  of  any 
subsequent  additions  of  water. 

Another  very  striking  result  from  the  above 

Table  is  the  large  amount  lost  beyond  the  root  zone  (assumed 
to  be  six  feet  deep)  in  the  case  of  the  Geer  tract.   This  is 
unquestionably  due  to  the  large  amount  of  water  used,  which 
should  not  be  mistaken  for  a  large  head  of  water.   It  is  but 
logical,  that  once  sufficient  water  has  been  applied  to 
satisfy  the  capillary  capacity  of  the  soils,  any  further  ad- 
dition of  water  will  increase  that  amount  which  penetrates 
past  the  sixth  foot  in  depth,  decreasing  thereby  the  percen- 
tage retained. 


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52 


Clay  Soils 

In  clay  soils  the  maximum  water  holding  capacity 
is  sometimes  limited  by  the  pore  space.   This  condition 
seems  to  apply  to  the  soils  described  below,  the  volume 
weights  of  which  were  found  to  be  very  high.   The  total  ex- 
ternal surface  area  of  these  soils  is  in  all  probability 
very  high,  to  judge  from  their  mechanical  analysis,  which 
showed  24.54  percent  of  total  sand,  40  percent  silt  and 
34.84  percent  clay.  Yet  the  quantities  of  water  found  in 
them  both  before  and  after  irrigation  were  extremely  low  . 

The  observations  made  upon  Clay  soils  are  present- 
ed in  Table  XIII  and  Figure  VII.    Figure  VII  is  based  upon 
86  six  feet  borings  and  Figure  VII  contains  the  averages  of 
568  borings.   The  Table  reveals  at  a  glance  the  striking 
fact  that  the  surface  foot  of  soil  was  appreciably  moistened 
by  the  irrigation  water.   It  is  doubtful  if  the  capillary 
capacity  of  the  wetter  section  was  entirely  satisfied;  yet 
it  held  after  irrigation  5.06  inches  of  water  or  enough  to 
fill  64.3  percent  .of  its  pore  space.   The  sixth  foot,  which 
was  kept  moist  by  the  ground  water  table,  contained  no  gravi- 
ty water,  but  eight-six  percent  of  its  pore  space  was  occupied 
by  capillary  water,  leaving  only  sixteen  percent  of  pore  space. 

The  Purdy  field  was  irrigated  four  times  in  the 


;od  19  Jew  ffurniixafs  arfct  alloe  ^elo  r*I 

no'  •)  aldl1      .aoeqs  9toq  ail*  ijd  be^lmx!   aairtidsisoa  al 

•     -  twcl9d  bsclioaeb  a^ioe   sdct-  od"   ^Iqq^  o:    amsse 

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rlolxlw  .aia^IaniJ  Itoinjeriag.'a  -lisrit   moil  33^^C   o*    *^3^  T?9V 
bns  .d-'JCia   *asoieq 'O*1   ^-rias   i^cto.i  lo  dnso-ioq  ^6.^2  bsworla 

ixi  bsutdft.  is^-3-.v  'iu  aat'rid-aaAr  iel      .^lo  drteoisq  ^S.I'S 

i 

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noqi;  boesd  ai  1IV   9iJj;9iri  .ilV  strjgi^  fon^   IIIX  sIcfsT  nl  £>e 

3iW   BKlsd-nso  .iw^W  6na   s^nliocf  *S3l   xie   S8 

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HOB  Ic   ctcol  oojaltae 
of>   ai    '         •    ^*aw  no 
aaw  rroWoaa  ie**9W-  siid"  lo 
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rlolrfw   ,^co1  ri^xla   arffi      . aoccs   yioq  a^     lo,  fcrtsoisq  <S.^<3  lili 
-Ivaig  on  b-enisctaoo    t«io'J3^  tsd'aw  _i?nwc- .          .    Y<^  J'siom  ^qdi  asw 
belqwooc   a.sw  eosqa   sioq  act!  lo   ^nsoiaq  xia-^rf^ie   ^xrrf  .tecfaw  ij* 

rfrk-^nt*!1      tTT''*  f  VG 

.908O3   9ioq   zo  jn  .  -->-    «i?osw   ^li-ixx^-j    \,i> 

nl  adnrW  "  ^^  Yfcii^   3iiT 


55 


season.   Of  the  7.08  inches  In  depth  applied  in  the  first 
irrigation  about  twelve  percent  entered  and  was  retained 
in  the  upper  three  feet  of  soil,  of  which  about  eleven  per- 
cent was  in  the  upper  foot.   In  other  words,  practically  no 
moisture  penetrated  below  twelve  inches.  "In  the  second  ir- 
rigation a  depth  oi  4.55.inches  was  applied,  nearly  all  of 
which  penetrated  the  soil  and  of  which  about  forty-five 
percent  remained  in  the  upper  foot.   In  the  third  irrigation 
a  depth  of  4.80  inches  was  applied,  of  which  approximately 
one-third  remained  in  the  upper  foot,  with  no  increase  below 
the  second  foot.   The  moisture  determinations  before  and  af- 
ter the  fourth  and  last  irrigation,  when  a  depth  of  5. 84  inches 

was  applied,  indicated  that  the  soil  became  more  impervious 
to  water  as  the  season  advanced,  for  about  sixty-six  percent 
of  the  amount  applied  was  retained  in  the  first  foot,  with 
no  significant  increase  below  that. 

The  soil  of  the  Tattle  field  is  similar  to  that 
of  the  Purdy  field,  but  slightly  coarser  in  texture  and  a 
little  more  open  and  permeable.  Moisture  determinations  were 
made  from  ten  borings  before  and  after  irrigation 
the  second  irrigation  and  nine  before  and  after  the  third 
irrigation,  a  depth  of  4.08  inches  being  applied  in  the  first 
case  and  4.16  inches  in  the  second  and  third  irrigation.   At 


bs  Jtlqqfi.rttqob.nl  agrfoni  80.7  artf  $Q 

bn^  beiaottS   d-neoieq  ovlewct    twocfs  ,  iiil 

cte   rloiiiw  lo    *Iloa  lo   cfesl   se^itt  isqqu  srf*  nl 
.  ab-xow  isii^o  «I      .^ocl  loqqjJ  sxl*  ni    saw 

we  lac? 


1  bnco33   9       -e        .as 

lo   ila  ^Iiasn.  .bailqcB   BBIT  asiionJ-.Se'.^ 

l  ^0corfi  riolrlw  Ic   bar.  Iloa   sri*  ps^Bi^snsq  ifolrlw 
*  -»rf*  ni      .?oo_1  leqqw  edo   nl  fcsniBnisi  ctnso'iaq 
rlelrfw  lo    ,nail^qa    SBW  aailonx  08.^  lo   diqab  B 


on 
-la  Bas.-sioletf  anoi^onlnweiab  etu^aloni  aif!      .rfool  bnoosa 

ssrtonl^S.S  lo  d*qeb 

smaoa-.  srW  cfcrid-  bs*aolb«I    ,69ilqqa   BBW" 

xi8-\>txis   j;;ccfs  'rol    .beortavbu   aoaiaa   srtt   33  IB^BW  ocf 
dctlw   ,-iocl  *eill   srf^  ni  b9nia*o«i   aaw  bs^lqqB   drtuorfts  add 

.jisnJ-  vYoied  aase-ioni  d-naolllnsia  on 
od-  i-Ilwia   ai   bie'll   si^ctisff   srl*  lo   Iloa   srff 


bno 

eitrtalpIL    .eldaeiffisq  bna  «sqo 

isd'lB  buB   siolsd  STUiliocf  us?  moil  e 

.  1m  1  ;  '••   9-f- 

srf-  '  •  rf^qab  a   tn    '        liil 

ol^je^lii:        J  i   asrionl   31.*  bnc    seao 


54 


the  second  Irrigation  ninety-three  percent  of  the  water 
applied  was  found  to  enter  the  first  three  feet  of  soil, 
about  one-half  being  retained  in  the  first  foot.   In  the 
third  irrigation  forty-four  percent  was  retained  in  the 
first  six  feet,  three-fourths  of  which  remained  in  the 
first  foot. 


lo   drn'dori: 


.cfoo 


SBW 


rioj: 


.<t< 


-f  o 


• 


••"•:  asrfonl  o--S 


- 


TABLE  XIV 


Irrigation 
Treatment 

T            1 

'Time  of  'No.  of 
'Sampling  'samples 

Moisture  content  in  acre 

Depth  at  which  sam- 
ples were  taken 

feet 

.5 

i 
i 

1.5  '  2.5 

i      i 
i      i 

3.5  '  4.5  '  5.5 

2  —  6  inches 

'Before  Ir*- 

i 

t 

t      i 
i      i 

'Mgation  ' 

14  i 

1.78 

2.03'  2.14 

2.46  '  2.37  '2.13 

Plot  B 

'After  Ir-1 

• 

t 

i      i 

'rigation  ' 

14 

3.26 

2.99  '  2.86 

2.69  '  2.75  '2.19 

'Increase  ' 

1.48 

.96'   .72 

.  25  i   .  56  '  .06 

i        i 

i 

i 

3  —  6  inches 

'Before^1 

• 

i 

i 

'rigation  ' 

21 

1.68 

1.93'  1.91 

1.80'  1.43  '1.29 

II 

Plot  C 

'After  Ir-1 

t 

* 

'rigation  ' 

21 

3.54 

2.99  '  2.82 

2.45  '  2.10  '1.86 

'Increase  ' 

1.66 

1.06'   .91 

.65'   .67  '  .57 

i        i 

i 

i      t 

4  —  6  inches 

'Beforeli*1 

i 

i      i 

'rigation  ' 

28 

1.76 

2  .  06  '  2  .  06 

1.87  '  1.59  '1.49 

Plot  D 

'After  Ir-1 

t 

i      i 

'rigation  ' 

28 

3.30 

3.06  '  2.75 

2.26  '  2.02  '1.87 

'increase  ' 

1.54 

1.00'   .69 

.39  '   .43  '  .38 

i        t 

i 

i      i 

4-7-5inches 

'Before  IP-' 

i 

i      i 

'rigation  ' 

28 

1.95 

2  .  16  '  2  .  08 

1.851  1.73  '1.63 

Plot  E 

'After  Ir-i 

i 

i      i 

'rigation  ' 

28 

3.20 

3.16  '  2.95 

2.60  '  2.40  '2.19 

'Increase  ' 

1.25 

1  .  00  '   .87 

.75"  .67'  .56 

i        i 

i 

t      t 

4-  -9  inches 

'Before  :&>' 

i 

.'      V 

'rigation  ' 

28 

1.85 

2.04'  1.92 

1.76  '  1.87  '1.59 

Plot  P 

'After  Ir-1 

t 

i      t 

'rigation  ' 

28 

3.17 

3.10  '  2.82 

2.52  '  2.57  '2.34 

'Increase  ' 

1.52 

1.06'   .90 

.76  '   .70'  .75 

t        t 

i 

i      i 

4-12  inches 

'Before  Ir-' 

i 

i      i 

'rigation  ' 

28 

1.91 

2.18'  2.05 

1.96  '  2.11  '2.32 

Plot  G 

'After  Ir- 

i 

i      i 

'rigation  ' 

28 

3.24 

3.30'  3.04 

2.99'  3.25  '3.41 

'Increase  ' 

1.33 

1.12'   .99 

1.03  '  1.12  '1.09 

i        i 

i 

i      i 

Averages 

'Before  Ir1 

t 

t      t 

'rigation  ' 

147 

1.82 

2  .  07  '  2  .  02 

1.95'  1.85  '1.74 

'After  Ir-' 

i 

i      i 

'rigation  ' 

147 

3.25 

3.10'  2.87 

2.58'  2.51  '2.31 

'Increase  ' 

1.43 

1  .  03  •'   .85 

.63  '   .66  '  .57 

i        t 

t            i           it 

r 


56 


55 

Lnches  per  acre  Foot  of  Soil 

Total  Wa- 
ter at 

Depth  of 

Total  percent- 
age of  water 
retained 

i     i 

i 

i 

6.5  '  7.5  '  8.5 

9.5 

10.5 

11.5 

0-6ft  '0-12it 

i      t 

t      i 

I         ! 

; 

i 

12.91' 
i 

1        •  1 
1          ! 
t         1 

, 

16.72  ' 
3.81' 

31.7         ! 

1         1 

. 

i 

<•            i 

t         t 

r     «  f 

10.04' 

i 

I 

i  i 
'.      t 

, 

15.56  t 
5.52| 

30.7         ? 

I         5 

i 

f 

!         1 
t          1 

'  : 

10.83' 
i 

- 

1         1 

1         t 
1         ! 

4 

15.26  ' 

4.43' 
i 

18.4 

1          t 

i 

1.47'  2.81'  3.24 
i 

3.63 

4.25 

. 

5.10 

11.40  '31.93 

i 

t 

2.21'  3.64'  4.18 

.74'   .83'   .94 
i      i 

4.22 

.59 
t 

4.52 

.27 

4.66 
.44 

16.50  '39.93 

5.  10*  8.00 
i 

26.7 

i      t 

- 

i 

i 

2.56  '  3.38'  2.84 

4.04 

4.53 

4.69 

11.03*33.07 
i 

I 

3.33'  4.08*  3.98 

.77*   .70*  1.14 
t      t 

4.49 
.45 

5.08 

.55 

5.15 
.46 

16.52  '42.63 

5.49'  9.56 
i 

26.6        '- 

i      i 

: 

t 

3.37  '  3.16  '  2.94 
i      i 

3.88 

3.86 

4.46 

12.53*34.20 

i 

1 

4.22  '  3.77  '  3.76 

.85'   .61'   .82 
i      t 

4.32 
.44 

4.32 
.46 

4.92 

.46 

19.  21  '44.  52 

6.68  '10.32 
i 

21.5         * 

i      1 

2.47'  3.12'  3.01 

t       i      : 

3.85 

4.21 

4.75 

i 

11.46  '32.86 
t 

t 

3.26  '  3.83'  3.97 

.79'   .71*   .97 
t      i 

4.34 
.49 

4.64 
.43 

4.91 
.16 

16.63*41.58 

5.17*  8.72 
i 

3 

.1 

:  Davis 

foot   of 
IB  increase 
xre   set 
)f  plot  B 
Decially 
?  content 
i  the   soil 

discrep- 
3  for.  A 
b  C  became 

accounts 

by  plot  C 
Lty  after 
st  were  mois 

likely  that 
lot  G  by  re- 
itational  wa 
tione  till 

irrigations 
stween  the 
i,  in  the 


V.IS 


'20 


•o1    : 


;    ?c. 

w  ;•    • 

v.ss  'oo. a  ' 


II4 


i        i 

ox.a'es.is1 


I 
I 

! 

_      | 
I  "I 

.£'  SS.£ . ' 


.    '35,  .',5*. 


5. IS   ' 


•  t£'  dS.. 

i 

!..£'  3S. 


. 
t 

c  . 


. 


56 


Experiments  at  the  Agricultural  College  at  Davis 

The  amounts  of  water  held  at  each  foot  of 
soil  before  and  after  irrigation  and  the  average  increase 
which  were  found  for  the  various  applications  are  set 
forth  in  Table  XIV  and  Figure  VIII.   The  soil  of  plot  B 
being  finer  in  texture  than  that  of  plot  D,  especially 
below  three  feet,  accounts  for  the  higher  water  content 
both  before  and  after  irrigation.   Variation  in  the  soil 
of  plot  B  is  probably  the  cause  of  an  apparent  discrep- 
ancy in  the  relative  amounts  of  water  accounted  for.   A 
comparison  of  plots  C  and  D  indicates  that  plot  G  became 
drier  before  irrigation  than  did  plot  D,  which  accounts 
for  the  greater  amount  of  water  being  retained  by  plot  C 
since  each  plot  contained  about  the  same  quantity  after 
irrigation.   In  plots  E  and  G  the  upper  six  feet  were  mois- 
tened to  their  full  capillary  capacity.   It  is  likely  that 
the  clay  loam  stratum  of  the  seventh  foot  in  plot  G  by  re- 
tarding the  downward  movement  caused  some  gravitational  wa- 
ter to  be  held  in  the  fifth  and  sixth  foot  sections  till 
the  time  of  sampling.   The  effect  of  the  large  irrigations 
of  plot  G  is  evident  in  the  great  difference  between  the 
moisture  contained,  before  and  after  irrigation,  in  the 


siicf  bete  no  id  63  Jit  1  'igctl-s  6ns  S'lolscf  iioa 
-solloqjs   ai/cliav  Sitf  iol  Jbm;o1  s'isw  lie  ' 
^   orf?      .IIIV  9i/j^i'5  ens  VIX  sIcfflT   ni 
39    ,0.  iolq  'io  cterfcr  njSiii   siL^xad'  qi.'rcanM  -Tt: 

*™^     „.»  «- 

.   'isiBw  igrisJtfl  adcf  •xol  actrtwoooa    ,^93!  ss'irii  wo 
.  .       '  ';   s.1.  nolcfeii^V      .noi-Tsgiiil  TacMa  Dxts   siolad  i 
-  •)  tfnsiflcpqs  HJS  "io   aai/so   sdi  vlciucfoTq  aJt  Q'  .d'olq 

-  fo'l  bactnuoooB  i9d".sw  lo   sctnwoiTtG   sv.td'olai   sfll  ni  v 

-  f  0  ctolq  d'BzW  .aad'soibnl  C  ana  D   aoolq  Ic  noai-. 

- 

• 

J  5  Y^  bsnls.ts'-i  gniscf  necfov/  lo   dra/o."afl  n 
.fl   Y^i^^8WP  Oi~n.jsa   sri-j"  J.uqcf^  bsnlBcfnop  dx. 
:ow  J33'i  xle  tsqqy  odd"  O  btis  2  s-lolq  al 
xi   2i   cfl      .vctlosaso  ^'iBlIicso   II.f/1   •il 

....  . 


57 


third  to  sixth  foot  sections.  The  twelve  inch  irrigation 
of  plot  G  caused  slightly  greater  increases  than  the  nine 
inch  application  of  plot  P  in  the  second  to  seventh  foot. 
The  upper  six  feet  of  the  water  content  curve 
in  Figure  VIII  plotted  from  the  averages  in  Table  XIV  are 
based  on  294  borings;  the  section  seven  to  nine  feet  is 
based  upon  120  borings  and  the  depth  from  nine  to  twelve 
feet  represents  averages  of  48  borings.  Adams  summarizes 
the  results  obtained  as  follows:/^/ 

"Not  counting  the  experimental  plots  at 
Davis  and  Willows,  moisture  determinations  were 
made  chiefly  on  15  fields,  of  which  13  were  of 
silt  loams  or  clay  loams.   In  the  case  of  all 
but  one  of  these  loam  soils,  for  which  one  the 
full  capacity  of  the  soil  to  retain  water  was 
not  satisfied,  the  average  quantity  of  irriga- 
tion water  retained  per  irrigation  in  the  upper 
six  feet  of  soil  was  equivalent  to  a  depth  of 
only  4.51  inches,  or  only  52.6  percent  of  the 
average  individual  applications,  and  only  .72 
acre  inch  per  acre  per  foot  in  depth  of  the 
soil.   Although  the  roots  of  the  alfalfa  pene- 
trate in  these  soils  to  a  greater  depth  than 
six  feet,  it  is  plain  that  a  considerable  por- 
tion of  the  irrigation  water  went  below  the  zone 
of  greater  root  activity  and  was  largely  or  whol- 
ly wasted. 

Considering  the  quantities  of  irrigation 
water  retained  in  the  upper  six  feet  of  soil  for 
all  of  the  field  for  which  soil  moisture  deter- 
minations were  made,  it  is  found  that  the  aver- 
age quantity  retained  in  the  lighter  and  more 
permeable  soils  was  .92  acre  inch  per  acre  for 
each  in  depth  of  soil,  whereas  the  clay  soils 
absorbed  an  average  of  only  .37  acre  inch  per 
each  acre  foot  of  soil,  or  at  the  rate  of  only 


.axfold-oss  tfool  rttxia  oA  biicfcf 


lo 


.'.B  o*  briooaa  »d 


9Visw 


aw  ad*,  to  ctsel  xle  i^qqir 

nl  asgsisvs   sii*  moll  bectd-olq  IIIV  eiwsW  nl 
ot  nev?a  noWosa  ecfet   jagnitocf  ^es  .no  baaed 
*  aoln  inotl  itfqefc   9ii*   5ns   a^nliocf  021     aoqu 
antsbA      .a^nJttod  8^  lo  easftisvB  scTn&aaiqsi 


'   a^olq  Isctnsmiioqxs   sii^t 

.ilflpi&*ei*)  aiw^sicm  ^swoIiiW  ferns 
si377  SI  rioiiiw  lo    ,abl9Jtl  21  .no  ^Ilsirfo 
Ii;'  lo   saco   srl^  nl      -atttfiol  YSlo  -10    amool   ctl 

-cmo  ;Ic>Mvr  -fol    ,Blioa  maoi   9aorf-')-  lo   aric 
»j8w  *xe^aw  niB*ei  oct  lioa   srCct  ic  ^lo^qJbo  11.01 
-jnJmi  lo   Y*i*nBUP  QB^av5  ®rl*    -.ba 
iscqju  sii.-t  nl  oolisaiTSi  rieq  b9fiij3*3fi 

j?  oct    tn3lfivl-yp9  saw  lioe  lo   : 


- 


10     B.Ct 


s 

.IiO3 


- 


• 


58 


2t  acre  inches  for  six  acre  feet;  due  to  their 
great  imperviousness  in  their  present  condi- 
tions.  In  the  surface  foot,  however,  the 
light  soils  retained  an  average  of  I.o4  acre 
inches  per  acre  foot  of  soil  as  compared  to 
1.71  acre  inches  per  acre  foot  held  by  the 
clay  soils,  this  being  in  accordance  with  the 
well  known  fact  that  clay  soils,  when  once 
thoroughly  wetted,  will  hold  much  more  soil 
water  than  soils  of  coarser  or  lighter  tex- 
ture. 

Averaging  the  quantities  of  irrigation 
water  retained  by  each  field  for  which  moisture 
determinations  were  made,  it  is  found  that  the 
maximum  quantities  retained  per  acre  foot  of 
soil  per  irrigation  were  1.02  acre  inches  for 
the  silt  loams  with  fine  sandy  subsoils,  .75 
acre  inch  for  the  silt  loams  without  fine  san- 
dy subsoils,  .78  acre  inch  for  the  clay  loams 
and  .49  acre  inch  for  the  clays. 

Considering  only  the  moisture  determina- 
tions from  the  surface  foot  of  soil  of  the  15 
farms,  it  is  plain  that,  in  the  case  of  the 
typical  silt  loam  soils  of  the  Sacramento  Val- 
ley, single  applications  of  irrigation  water, 
exceeding  depths  of  one  to  one  and  one-half 
inches  per  foot  in  depth  of  soil  it  is  necess- 
ary to  moisten,  accomplish  no  useful  purpose. 
While  the  typical  clay  loams  and  clays  of  the 
valley  will  retain  against  gravity  in  their 
normal  growing  condition  as  much  as  It — 1  3/4 
acre  inches  of  irrigation  water  per  acre  foot 
of  soil,  over  and  above  the  amount  normally 
found  in  such  soils  under  Sacramento  Valley 
field  conditions,  that  amount  of  irrigation 
water  will  not  be  absorbed  by  these  soils  un- 
less it  is  applied  very  slowly. 

The  wilting  percentages  for  the  Sacra- 
mento Valley  soils  under  investigation  ranges 
from  10.35  in  the  case  of  the  silt  loams  of 
the  experimental  irrigation  tract  on  the  Uni- 
versity Farm  at  Davis,  to  16.59  in  the  case  of 
clay  loam  on  the  same  tract.   The  average  wil- 


. 

• 

hi      -s. 

• 

,^  .     _A».X«       -<  W    **-j*.^^» 

lo  ctool  9*108  iQq.asdoni 
;  Jool  9ios  isq  i  l?.l 

.^.j."      •   .      .  JOOB  rtJ  gni^d  alxlcf '  *allo_p    .. 

e>r  fr     ve is   i  •  :  f   r-o^i 


,  :t  rloc/m  blori  II1» 

"1  ic  1S8TU500  lo'alioa 


-  brtfjol  ai  d"!   ,9i)«ffi  ariaw 

•jo    :  -10J3  ieq  LaniBd'9ri   aslcJ'icJTtsi/p  fawnilXBm 

10!  36iloni  9103  20.1  ais»  aoiiaal'iii  «iaq  Iloa 

oV.    «3lloacfwa  ^fcrusa   ariil  rttlw   airmol  His   edd 


-/£lo  ail*  ici  rioiil  S^OJB  8V.    .sllosdwa 


-. 
51  sn'd-  lo'Iloa  Ic  ^ool  90  situs   erli  mo-il 

d^   lo   33flO   ©d^    01   »^ail*  rtielq  el   ^1    «8Rrxa' 
amaios^  9i»  lo   aI±oB...na'ol   ills    taolq^ 
HoJt-tBgJtui  lo   anoi^soilqqa   eAgala    , 
anc  5r^   anc   oJ   suo  lo   siUqeb  s«lfiisec 
al  Jl  1102  lo  tfJcreb   nl  dcol  "isq   .. 
q  iJJlssw  on  cEsilq^oooc    ^jtaiom  o^ 
rf^  lo   s-iBlo  bna  airusol  \-B!O  Isoiq^   s;* 
"ilsrict  nl  ^Ivs'is  tfenisga  nifivtei  lliw 
^\3  I—  il   a  a  iloum  sc  £|o±tibooo  salwoig  I 
1  9ios  i9q  i»*flw  rrcJt:       Mil  Ic   aaiforci   e 

3  'ISVO     ,1 

' 


' 


i       o   ci 

le  ad  '  • 

i  saol 


59 


ting  percentages  for  the  several  types  of 
soil  under  observation  were  10.65  for  the 
silt  loams  with  fine  sandy  subsoils, 
15.12  for  the  other  silt  loams,  14.21  for 
the  clay  loams  and  13.06  for  the  clays. 
The  approximate  quantities  of  water  neces- 
sary to  apply  to  thoroughly  dry  soils  of 
the  types  listed  to  bring  tne  moisture 
content  up  to  the  wilting  points  given  are 
in  inches  in  depth  per  foot  of  soil,  1.5 
for  the  silt  loams  with  fine  sandy  sub- 
soils, 2  for  other  silt  loams,  2.3  for  the 
clay  loams  and  2.6  for  the  clay.   The  op- 
timum percentage  of  available  soil  mois- 
ture for  Sacramento  Valley  alfalfa  soils 
over  and  above  the  percentage  at  which 
wilting  occurs,  seems  to  average  between 
4  and  Q%.   This  is  equivalent  to  depths  of 
from  .6  to  .9  inch  of  irrigation  water  per 
foot  of  soil  for  loam  soils  and  of  from  .7 
to  1.2  inches  per  foot  of  soil  for  the 
heavier  clay  loams  and  clays. 

Alfalfa  planted  on  very  open  and  very 
impervious  soils  should  be  irrigated  more 
than  once  between  cuttings.   This  is  nec- 
essary in  the  case  of  the  open  soils  because 
of  the  inability  of  such  soils  to  retain  all 
of  the  moisture  needed  to  mature  a  crop,  and 
in  the  case  of  the  impervious  clay  soils  in 
order  to  accomplish  deeper  penetration  of 
the  irrigation  water  into  them.   In  case  of 
the  latter  soils  it  is  very  desirable  that 
the  moisture  supplied  by  winter  rains  shall 
be  supplemented  by  irrigation  water  suffici- 
ently early  in  the  spring  to  prevent  drying 
out.   The  frequent  use  by  irrigators  on  such 
soils   of  a  soil  auger  is  to  be  urgently 
recommended,  the  investigations  having  demon- 
strated that  penetration  of  irrigation  water 
into  the  clay  soils  is  very  much  less  than 
irrigation  usually  realize. 

It  will  be  noticed  that  the  curves  plotted 
from  the  foregoing  result  do  not  bear  the  same  character- 


10!   e 
w'rtcjtd'  'o  lebnu 

dtflw   atr_ecl  31  la 
lertfo    srtt  «iel  SI  .  51 
1   '  '--ol   ^sJo   3-:^ 

aB0p  sctKirdxo'iqqjs   orfT 
;    oct   ^Zqqc   Oo    visa 


.u  novi..  afrnloq  -^liJlivr  srW   ocf   qL- 

a.  I    ,  r'ios  'io   *ool  i3q  xWqsb  nJt   a^^ro.nJ 

-cf.f/a  ^fcnjsa   anil  fitl^   arose  I  *J  !e   *rfd 
aclj   tol  S.2    tarrt£ol  d-Ii^  10' 

-GO   srfT      .vBlo   sd*  10!  8.S  bns   aniaol  ^ei 
-eiom  lie  a   sid^Ixsva  lo   s 
allca   slisllB  ^slicV  o-JriS 

ioinv:  ^B  o^B^naoisq  ail*   dvods  brrs  'i 
naow^sd  sgii^ava  cj   smase    taiwooo  grtiJ 
'io   arld-qsb  o*   toslsvii/pe  al  .3irfT      .^3  6n--i 
sq  --led-sw  nold-egJt-iii  -lo   doni  6.    o*   6.    UKrrl 
.  "moil  Io  SOB   sliQe   nTBol  ioi   lioa   'Io 

--ic'i   lioa   Io  -creel  isq  asifonl   3.1   oct 


fteqo  "'f^v  ao   bsf^-q 
3-rofti  b  9-^375  .ttii  scf  ftlja:bi-a  aiioa 


JLioa  naqo   srH    Io   9830    ?^Ict  rJ 
i  ocr  alioa  rfe.aa  Io  ^'  lie 
fene    tqorfo    o  etifctB«t  od"  bebssn  si^J-aicin 
nl   alioa   T^.elo   aL'oivisqrrsi   Silct  Io   SSBO   9dJ 

"io  noJttsi*9n»q  laqssfi  dsilqmoooa  bet  isbio 
io    9-iG  o  al"     .fnsifd   odnl  a^ctsw  noj 


do  i/a  no   a 


.       • 

;tcic    2     ' 
fYft-  .  ' 


60 


istics  of  an  abrupt  diminution  of  soil  moisture  at  a 
fairly  definite  depth  as  the  experiments  quoted  previous- 
ly did.   The  explanation  of  this  is  to  be  found  in  two 
factors'.   In  the  first  .instance  the  initial  water  content, 
especially  at  the  lower  depths,  is  much  higher  than  in 
the  first  case,  where  practically  air  dried  soil  was  used. 
This  will  have  the  effect  of  decreasing  appreciably  the 
frictional  resistance  that  the  irrigation  water  has  to 
overcome  in  its  downward  penetration,  since  the  initial 
water  distributes  itself  as  films  round  the  soil  particles. 
The  water  that  is  added  therefore  is  under  a  much  smaller 
influence  of  soil  affinity  and  the  other  film  forces. 
There  is  therefore  a  greater  tendency  towards  the  sliding 
off  from  the  already  existing  water  films.   The  higher  the 
initial  percentage  of  water  present  the  greater  is  the 
amount  that  will  penetrate  downward. 

In  the  theoretical  diagram,  if  the  initial  water 
percentage  is  kf..  the  amount  of  water  that  will  be  dis- 
tributed uniformly  is  cde,  whilst  if  the  initial  percentage 
is  kg,  the  excess  amount  of  chj--and  the  resulting  curves 
before  and  after  irrigation  will  be  as  shown- -the  two 
curves  converging  with  an  increase  in  depth.   In  view  of 
the  results  obtained  from  these  experiments  and  the  assumed 


lOKi  ilos   lo  nol^ualfalo  (J-qwids  OB  lo   ED  Ida! 
-3juolV9tq  berfotfp  acffls-ul-i  3.^x0  sxio    se  fl-Joso  a^iotlsfc  ^1^1 
owd-  nJt.uouol.ed  ctf  ai  eiitf  lo  flottMWlqxa  aJT     .Jblfc  ^1 

d-xts^noo  is^xvff     tiitini  stiJ   aons^aai.  ^siil  9£lc>   nl 

nx  rtsii^  'isri^lxl  riowtft  al   ta^Ilosb  tsvrol   9dJ  ^ta  -^iiclosqas 
ii-  asw  lloe  belrci)"  iJt«  ^IIaol*oai«   9iadw   -eeao   ia-i 

Ylcfj3io3«iqqs  •4rilasari;39&  lo   uos'ils  .scl^   evsil   lliw  alxfT 
asxf  t3?BW  nol.is^jtiti   sxid-   tc-IcJ-  •  9oxr«.i3i39i  isnoJtcfrolil 
JIrti  edi   son.ta    ,  noi.-t^ij-sneq  6ijewnwo£>  adi  nl   s.:.iooTfsvo 
HOB   ai-d   ont'o^   a.^tlil    as  llsail   39*.oclli,iaib  ^actsw 
/3.Ti3  rIo0f:T  Q  isbnw  ti   g^c'Iana^   bso;:.--    si    lo-rld"  aactfiw   erIT 
.39010!  fitl.fl  i&r.'-'to   c?/t   bn-5'  •,;•?!«  I'll  3   Iioa  lo    aonDwJlni 
'lia  3iW   d  :.>•!£;  7/0  ct   -.on^brtS-}      rrcteo  c,a  A   siolsigiid"   al   o-isaT 
j-I^irf  edT'     .arrrll'i  tel^w    v'^^slxe    '^Bg'ilfl   9;fd-  moil  .Tlo 
.i.i  al   Tscf  '-3^3  -srfd'   d-nsaeaq  •isd'^w  lo    s^ed-aao^eq  Islcflnl 

nag  IlJTw  d'arlcJ'   jnwc;,t8 


q   Lsid'lnl  artt   11.  islirivr   ,e&o  al  ^lnrrollnw  fis-tj/dlT:^ 
30V1UO  ^nltl/jaei  sifct  bn«--{,rfs  lo   in.croffi';   c-.asoxa   siict   .  ^3i  el 


lo  w.9lv  nl      .rf^qab  ni   aeaaapnl.  n  T  ^£tl"ji9vricc   a-avitro 


60a 


theory  it  follows  that  it  is  not  the  soil  moisture  which 
distributes  itself  according  to  the  root  system  of  the 
crops,  but  it  is  rather  the  root  system  of  the  crops  that 
distributes  itself  according  to  the  distribution  of  the 
soil  moisture. 

There  is  a  very  mistaken  fallacy  abroad  (especi- 
ally is  this  the  case  in  alfalfa)  that  the  soil  should  be 
wetted  to  the  depth  of  the  roots,  and  alfalfa  being  deep 
rooted,  sufficient  water  should  be  applied  to  penetrate  to 
that  depth.   But  since  it  is  a  well  known  fact  that  the 
roots  rather  distribute  themselves  according  to  the  prevalent 
moisture,  it  follows  that  any  excess  water  specially  applied 
.  for  deeprooted  plants,  say  below  the  sixth  foot,  is  practic- 
ally an  entire  waste.   It  has  been  noted  by  various  authori- 
ties that  on  an  average  the  following  percentages  of  the  en- 
tire root  system  for  alfalfa  penetrate  to  the  depths  indi- 
cated. 

1  foot  deep  27  percent 

2  feet   "    43    " 

3  "        12    " 

4  "    "    10     " 

5  "    "     7     " 
beyond  5   "    "     1    » 


-T-o-Dcrsg)    baotdB   vosliel   aa^B^fc-ira  -£-1^  *  si 


i  '\   vj     d"O.S'X    CIWO£pl    Ii3tf    S     3X 

9x1*  o^   ^alb-iooos   asvisancs 
Ilciceqa  t9ctsTr  aaeoxa 
al    .  ^oo'i  dcr:<J:e   sii.-t 

yd  bs^on  rtaed   aed  ^1      .9 


91 


B1 


II^HRSI 

mm\ 


51 


CHAPTER  V 
CHARACTER  OF  SOIL  AND  SUBSOILS 

Apart  from  the  actual  texture  and  structure 
of  the  soil,  there  are  various  conditions  that  are  met 
with  which  influence  the  application  of  water  to  a  very 
large  extent.   Foremost  of  these  is  the  layer  of  hard 
consolidated  soil  particles,  known  as  hardpan.   See  Fig. 
IX. 

Hardpan  is  the  result,  to  a  large  extent,  of 
soil  weathering.   The  finer  the  particles  are  broken  up, 
the  nearer  do  they  approach  that  class  of  soil  termed 
clay.   The  particles  are  subjected  to  percolating  water, 
and  the  soluble  constituents  may  be  taken  into  solution. 
Thus  we  have  solutions  of  sodium  carbonate  and  various 
silica  salts,  associated  more  or  less  with  other  products 
of  rock  decomposition.   It  is  in  the  surface  soil  that 
these  solutions  are  chiefly  formed.   And  according  as 
their  descent  into  the  substrata  is  unchecked,  or  is  li- 
able to  be  arrested  at  any  particular  level,  whether  by 
pre-existing  close  grained  layers  or  by  the  cessation  of 
the  rainfall,  the  subsequent  penetration  of  air  and  evapora- 
tion of  the  water  alone  by  shallow  rooted  plants,  may  cause 
the  accumulation  of  the  dissolved  matter  at  a  particular 


9-I.J     .  ' 


ICf|:         .  Cfn< 


:x»c3  o<n 
a^'oiisv  bns 

s  «i3^o  rfdlff  aeal'ic 
lioa  sosliwa  erl^  nl 


-slo   ^srfd    £foeoiQ.qs  ^srtd 

i  bs^oscfwa  91^  asIpijJriaiii  $rIT      ."^ali 


62 


level,  year  by  year.   The  action  is  largely  accentuated 
by  the  filtering  action  of  the  minute  clay  particles 
which  have  originally  been  washed  down.   The  water,  charg- 
ed with  these  minute  particles,  precipitates  them  whilst 
passing  through  the  accumulated  layer  already  laid  down  by 
the  percolating  water.   It  therefore  is  of  an  accumulative 
order,  the  greater  the  amount  of  colloidal  matter  washed 
down  the  more  extensive  will  be  the  filtering  action  and 
the  thicker  will  be  the  resulting  hard  impervious  layer. 
Once  the  layer  has  become  impervious  the  descending  water 
is  either  used  up  in  transpiration  by  the  plants  or  by 
evaporation  into  the  air.   The  dissolved  salts  are  hence 
crystallized  out  and  will  act  as  a  cementing  agent,  be  it 
siliceous,  calcareous  or  ferruginous  in  the  consolidation 
of  the  accumulated  layer.   The  ultimate  result  is  a  hard, 
consolidated  layer  known  as  hardpan. 

According  to  the  cementing  agent,  hardpans 
will  either  be  an  iron,  lime  or  siliceous  hardpan.   The 
iron  hardpans  are  exceedingly  heavy  and  much  more  compact 
than  the  lime  hardpan.   It  has  the  fortunate  characterictic 
that  when  once  broken  up  by  dynamite  or  some  other  method, 

there  is  but  small  danger  of  it  reconsolidating.   On  the 

lime 
other  hand/nardpan,  which  is  readily  recognized  by  its 

lighter  colour  and  by  its  rapid  disintegration  by  dilute 


ew  fissc    T^wn^o   averi  rfoifiw 

ild1  ilctir  bs 


>rfo  <=»••<  e    .a         '  •>''• 

>  O    1  VJ          •    M  *  J  -  *i 


.isd'ew 


flooA  jjnis  ori.t   3d  IlJtw  svisne^xs  sioia  srftf  xwob 

oivisqjni  Mi-n  30  Wins  91   srf^t   sJ  Illw 
nsoaai)  Qrf*  aucivasqmi  emoosd  a 

^Cf  -io   s^nfllq  9^  ^J  noi-tJB-xIqarwi*  nl   qw  b.«au  i-arttls  ai 
son»£l  9iJ3  a*Ifls  fiovloaslb   9-T 
il   ecf   ^o«sa  s«i*nsnteo   B  SB   C^OB 

A*.  \\>V-  vi"V». 

feilosnoo   wtf  rxi  Bflo«±^*«wl-  rro   auoe 

..Msri  a   el  JlJre'&i  9*«raJt^lM  grfT      .I^B!  Be^sXiR^ooB  ei!*  lo 

.nsqbtan  ae  nwcml  -i^^X  b»*BDlIoaiieo 

.*asBe  inl^neweo   sd*  o^  gru. 

auceolXJ^a  «no  will   ,£toil  as  »d  writfls  Jilw 

-oo^Y*      af'R  rOll 

...-TB  ^vBsn  vi 

~jj;j"xoi  S^   afiil  ^1  stftiX   93-3  *- 

.^TA.  «x  '-o-s-  t-ttismrfs  :of  sono  iio:!^  ^ 


63 


acid,  may  be  reformed  by  the  descending  water  in  time  to 
a  second  hardpan  layer.  The  iron  and  silica  salts,  once 
precipitated  out,  do  not  readily  redissolve. 

It  is  fairly  well  established  that  the  lessen 

-//,»•'« -.,•>-• 
the  rainfall,  the  smaller  the  depth  at  which  hardpan  is 

found  and  the  softer  in  texture  it  probably  will  be.   In 

general,  hardpan  may  be  encountered  from  twelve  to  twenty- 

_ 
four  inches  below  the  surface.   If  at  a  greater  depth,  it 

will  usually  be  due  to  the  formation  of  a  more  recent  soil 
layer  on  top  of  the  original  surface. 

It  is  evident  that  when  such  an  impermeable 
layer  is  allowed  to  remain  near  the  surface  it  produces 

serious  results. 

,^,f . 
(1)  By  the  failure  to  absorb  the  greater 

part  of  the  water,  thus  permitting  it  to  flow  to  the  lower 
part  of  the  orchard  and  out  into  the  adjoining  lands,  (2) 
by  facilitating  sideway  surface  percolation  from  the  fur- 
rows and  exposing  a  greater  area  to  evaporation  by  the  heat 
of  the  sun,(3>  by  holding  the  water  near  the  surface  and 
thus  causing  its  loss  by  evaporation  before  the  soil  is 
cultivated,  (4)  by  preventing  access  of  the  water  to  the 
roots  of  the  trees,  if  any,  lying  below  the  hardpan,  (5) 
by  preventing  proper  ventilation  and  aeration  of  the  sub- 
soil. 


ef>  extJ  ^cf  ber.nolsi  sd  ijs 


u'.;        o 


j?l   ciid  dnrf-t  fostfal-I a'edss   liaw  ^L^iffl   2! 
el  ruaq.b'xs.u  riolifv;  do    iidqaJb  srid  naJIiiwa  ed*- «ll«lal»i 
01      . eel  lllw  vlcfodoiq  dl  aif^XBd  ril  isdlca  a^i 
-ijdne^d  od   9v4*v/-d  .tto'i'i  bs 

dl   ,i{jqsb  Tsd'&s'is  3  d,-j  11      .  eoe'n^a   std  wolacf  aarlonl  iirol 
lic<3  drisos't  9*iont  s  lo  rtcid^fmol  arid'  od   swb  scf  vilctfew  Illw 

'iiigiio   9£fd   lo   qod   .' 
iid  dns&ivs   al.  dl 
:nan  nisnts-i  od1   ftswoIXs   al 


cfioadc  od"   ^iilici  and  ^d     (I) 

iswol   arid   oj   well  ol  di  gnlcJ^lnnaq  awxid    ti9^sw  arid-  "io 

(Si  \abrxBi   3nlnlc'.;/£    ^xid   odnl  dro  bne  bisrioio   erid  lo 

-iwl  slid    nwil  aci:  ..'looieq'  90*lii/a   -^waiile  snidB^tllO 

-florl  arfd"  -^cf  nolcraioqev*  ocf   saia  isd'aeia  a  gfllaoqxe  &no 

d*  isen  lodsw  eta-  gaib  oil  ^d  ^5K 

ft: 
al  IJtoa  eitt  eiol-ed  rxoidsioqavs  YCf  saol  a*l  gnlax/ao   e. 

od  lad's-*  srid  lo  a 


.l±oe 


64 


Soils  underlaid  with  hardpan  should  therefore  be 
irrigated  very  continuously — a  more  moderate  quantity  more 
frequently  applied  than  for  deeper  soils  being  the  best 
practice.   It  may  often  be  profitable  to  blast  occasional 
holes  through  the  hardpan  to  serve  as  outlets  for  the  excess 
water  that  stands  on  the  hardpan.   Such  blasting,  to  be  ef- 
fective, should  occur  frequently,  in  which  case  the  process 
becomes  highly  expensive.  Before  undertaking  this  measure, 
it  certainly  is  advisable  to  make  a  thorough  examination  of 
the  extent  of  the  hardpan,  its  nature  and  depth  and  the  type 
of  soil  underlying  the  layer.   If  underlaid  by  a  heavy  sub- 
stratum like  clay,  blasting  is  inadvisable.   The  extent  will 
not  so  much  be  that  of  opening  the  soil  by  cracks  and  crevices, 
but  rather  that  of  forming  a  watertight  compartment,  the  clay 
being  compacted  all  round  by  the  force  of  the  explosion. 

The  effect  of  the  texture  of  the  subsoil  on  the  use 
of  water  is  quite  material.   A  heavy  soil  strata  occurring  at 
depths  of  three  to  six  feet  is  of  much  aid  both  in  retaining 
moisture  and  in  the  cross  percolation  of  furrows.   The  heavy 
subsoils  are  in  general  not  entirely  impervious  to  water,  the 
irrigation  water  penetrating  them  but  the  .rate  at  which  such 
water  escapes  by  deep  percolation  is  materially  reduced  so 
that  the  moisture  is  held  for  longer  periods  within  reach  of 


gcf 


£>ii/c£fe  nsqfctBa  rfd'lw 

9fiont  e  — 

*39d  arid-  ^nled   eIJtos  leqssc  'iol  nsiid-  £>allqqj3 
iBnoiaeooo  ctasia'  od-   slctectlloiq  9d  uecTlc  -^sm  *1 
aasoxs  sd$  'io1   sd'al.iwo   ae   avtaa    act  nsg.En.sd  snct 
-Is  9d  ol    ^grtid'ajsicf  rfbx/C      .K&vjjnati  adct  no  ar-nsda 


eeioil 


eaao  ; 


nl 


iwooo 


lo 


airict 


£>HB 


t  evict  09! 
asmooscf 


xfeiJo^or;d•   e 


ocj-   alo^s 


a 
s/±ct  'ic    drisctxe 

lioa  lo 


lo  d-tulj   so' 
LTic'i  'io   J-BiI 

ilfi  £}9ctoeqmoo 


os 


-dua   ^vj39il  ^  YO/  ii-jsiisibnj/  11      . 
IlJtw  chisctxe   ^:fr      .  slc^iaivb-anl   al 
,aeoi:v9ric>  feris  a:-;oe'io   ^d   1."  :t 

valo   9ii3-    ,  d-nsmJ-ijaqnioo  d-iisid-isctfiw  s 

.nclaofqr.e   9ili  'ic   9010!   s&j 

9ao'  erfcf  no    I^oarJ^a   OiU   "io    err^xect   srict   Ic   Jo9lle 
j"fi  ^niiiijooo   act_vjya   lies   *^ve.9d  A      .Ici'jcsd'a.Ti  sctiwp  al 
^ninJBtsi  ni  dtfod  &!B  rioJOTT  lo   E!   igel  xla  od    9Sirld;  lo 
il  ar£T      .  swoiitfl  Ic   nclcH'Ioo'iaq  aao'io   »£fct  fli  bne 
ts*jaw  oct  awciv^aitrl  .^Xa-ildrsa  ^on  Isiaxies  ni  ois   alicedtra 


lo 


-30 


ic 


-isritf 


65 


the  plant  roots.  Such  a  condition  is  more  favourable  than 
an  impervious  layer  like  hardpan  as  in  the  latter  case  great 
care  is  required  to  prevent  water-logging  of  the  soil. 

Where  there  is  no  heavy  subsoil  to  assist  in  cau- 
sing lateral  percolation,  the  ease  with  which  moisture  can 
pass  downward  lessens  the  extent  of  lateral  percolation  and 
a  closer  spacing  of  furrows  is  required  to  secure  an  even 
distribution.   A  large  part  of  the  water  applied  may  also  un- 
der these  circumstances  be  lost  by  deep  percolation  in  the 
upper  part  of  the  furrow  before  the  water  has  reached  and  ir- 
rigated the  lower  portion. 

When  the  soil  is  underlaid  with  gravel,  or  if  gravel 
seams  pass  through  it  within  ten  feet  of  the  surface,  the  nor- 
mal distribution  of  the  soil  moisture  is  disturbed.  If  gravel 
is  mixed  uniformly  with  the  soil  from  the  surface  downward,  or 
at  varying  depths,  the  soil  may  be  looked  upon  as  being  contin- 
uous so  far  as  the  distribution  of  water  is  concerned. 

When  water,  moving  downward,  reaches  a  layer  of  loose 
gravel,  the  descent  of  the  moisture  film  is  first  arrested, 
then  the  film  is  -thickened  until  the  lower  soil  pores  are  filled 
and,  if  irrigation  is  continued,  gravitational  water  drips  from 
the  soil  into  the  gravel  below.   The  water  which  thus  passes  in- 
to the  gravel  cannot  move  back  by  capillary  means  and  usually 


narf*  ©Idsii/cv.sl   eiora  al  noicriDnco        rio«8      .etfooi  Jtnslq  arid 

nl    as   neqlii&ii  6iiH  te^al   awclvisqml  lie 
.Iloa   sr#    lo   ryiissof-ioJaw  tfn^vefq  o«    bgiltfpdt  si   eiao 
-wao-nl  d-elaas   o$   Ileadwa  xvB^xi  on  sJ:   siarW  e-xerflT 
HBO  siijtfaloai  doliiw  xiJxv  eaa©  afltf    .naiifiloowq  Iflne*2l  gnla 
£>ns  noWalooisq  XBisctoI  "lo   Jaetfxo   arfd   ansaasl  fctawdwoJ     aesq 
H0vs  nfi  etjjose  oct  X>eniup9«x  el   ewo-i-utt  ^o   anlo^qa  teeolo  fl 

< 

-nj;  oals  ^flm  bellqqe  isctsw  edct  lo  *iaq  egisJ.   A      . 

sri^  nl  noWe-Ioo**^  qesb  ^  ^20!   eJ  eoon^a^o'ii 
-il  bnJ3  bsrioaei  aaci  locta.w  and.   o'lolocf  Yron-ro't   9iU  "10 

is  we! 


11  ^o    tl9Vi?ig  rlcHw  blel'iabrtc/  al   l.'-.cs   aud" 
-ion  oi-y    ,90BliwB   9r«   lo   C5-S31   ne*  nlildiw  -11  ^g^ 
I3V31.S  II      .bscfiurfalb  2!   e-utfaloia  lioa    eiW  lo  riold-i/dii^s-lj 
10    .bi.ewrrwofo   so^/lii.ra   9;ii   nto'M  iioa    yiii  ri^lw  .Ylirnolim;  baxlm  el 
a»i   npqv  befool    ocf  -?Btn  Jlloa   srtt    tsri*qofj 

a::   is^isw  lo  nclludlid-alb  afit*   ae   nsl  oa 
saocl  lo  i9"i-3l   a   ssrioan   .biawmrob  anivom   ,i»d-sw  necIW 

.bs^aoii^  d-aill  al  fftlil   9urtaic0  otl*  lc  tfrteoseb   exit    . 
bellii  a*j2  ayioq  Iloa  i9*ci   94^  IWnu  beaa^ol4J-  al  mill 
noil  aqlib  IS^BW  I^aodd^lvsi^   ,b9WHl<tnoo  -el  nclis^liil  11    * 
-rtl  aaaesQ  awrfi  £told¥  le^aw  9ilT      .wolsd  iavGig  DriJ  orfnl 

boa  BflBaic  3         &»<*  »VP^  Jomiso   levBi3  ertt  o-t 


66 


drains  away  into  the  subsoil  and  is  lost  to  the  plant. 

Soils,  in  which  such  gravel  seams  occur,  should 
therefore  be  irrigated  lightly.   Not  enough  water  should 
be  added  to  allow  any  part  to  move  into  the  subsoil.   Un- 
der such  conditions  more  frequent  applications  of  water  be- 
come necessary. 


oct  ctsol  ai  fens  HoacUra   erf*  o*nl  ^aws 
dowa  a'olriw  01    ,ello2 


svom  o.J    ^-xaq  ^/IB  woXI*  o^  f>sS6fl   9d 
lo   anoliftsllqqfl  d-^swpeil   enom  anoim>xioo  rio;ju   -^9b 

.iKaasosn   srnco 


67 


CHAPTER  VI 
EVAPORATION,  PERCOLATION  AND  SURFACE  WASTE  LOSSES 

The  water  applied  either  by  precipitation  or  by 
irrigation  to  the  land  is  disposed  of  in  two  ways:   part 
of  it  runs  off  and  is  wasted,  and  part  of  it  soaks  into  the 
ground.   This  latter  part  is  disposed  of  in  three  ways  (1) 
by  plant  transpiration  (2)  by  evaporation  and  (3)  by  per- 
colation. 

In  irrigation  it  is  the  object  to  reduce  the  sur- 
face run-off,  evaporation  and  percolation  losses  as  far  as 
practicable,  thereby  keeping  a  maximum  amount  of  the  water 
applied  stored  in  the  soil  within  reach  of  the  roots  until 
such  time  as  it  is  needed  by  the  plant. 

Evaporation.   Immediately  after  the  water  has  been 
applied  to  the  soil,  evaporation  begins  at  the  surface  and, 
in  time,  if  not  checked,  the  loss  in  moisture  will  be  felt 
throughout  the  root  zone . 

The  movement  of  water,  as'  already  explained,  is 
from  the  thicker  to  the  thinner  water  film  or  from  the  wet- 
ter to  the  drier  parts  of  the  soil.   When  therefore  the  im- 
mediate top  layers  of  the  soil  lose  their  moisture  by  evapora- 
tion, there  is  a  tendency  to  partly  replace  this  loss  by  an 
upward  movement  of  water  from  soil  particle  to  soil  particle 
from  the  wetter  subsoil. 


IV  .JO 


dia.  :e\'«w  owd  nl  Ic  baaoqs   a   n* 


eiq  v-   i9*-rdi9  &  isdaw 

d.  od- 

add  otni  a^oa  it  lo  *isq  bns    .bsitaew  ai  5ns  llo  aaxn  *i 
U)    a^w  991,  i*  ni  lo  Dsaoqaib  a  I  ctiaq  ledrfal   sixfT 
-isq  ^   tS)    bns  nciiaioqBvs  ^d  (S)  '  Hol^ailqerwi*   *nslq 


-IJJ3   srict   90-ubsi  od-  cro3f,cfo   arid1   ai   di  aoide3itii  ni 
BS  IB!   SB  ssaaol  no'ld-jBloO'isc   bnc  ncl-^aioqavs    / 
IQ^BW  su'cr  lo.  *nbo«ta  nujfiiixam  a  gnlqeeil  ^cJe'ierid 

3^0  ^ 

aitt   '^d  bebssn  ai   3i   SB  siplct  rlo^s 


tbns   soc'liui   9dd  dj   sniped  noidsioqsvs    ,Iioa   9xJd   od  bsilqqs 

d-131  sd   II iv;   siirfslom  ni   saol   oiid    ,bsj(oerio   ^on  'ii    ,emil  ni 

ai   ,benir:Iqx9  TfbB9il3  ae    «iodaw  lo  dnsmevoin  sdT 

•       r    *  f   •  A  »i*^f-  r!'*^         r*  fS^*        fff^iff  *T 

f  sild  mo'i'i  10  ffdi'i  lodew  isnniiid  sad  od  is^oiiio    saff 
-mi  er&  eiolsisrid-  n«rIW      .lioa   arid  lo  sd"isq  i^lib  arid   od  i»d 

?d  9'iwdaiom  lisrld   gaol   lioa   &d$  lo  ais^s!   qod 
Y5J  •  >aad   ^   ai 

>drriY  lo    J  ORt 

.•:vr:.i 


68 


As  evaporation  proceeds  from  the  top  soil,  the 
water  in  every  soil  layer  diminishes  to  the  full  depth 
of  the  root  zone.   Dr.  Widtsoe  likens  the  action  to  that 
of  cotton  packed  loosely  in  a  box.   By  removing  a  small 
quantity,  the  remainder  expands  occupying  the  same  volume 
as  before,  but  in  a  looser  condition. 

In  soils  a  similar  condition  is  met,  when  part 
of  the  moisture  is  extracted,  there  is  a  thinner  moisture 
film  condition  throughout  the  entire  mass.   But  the  de- 
gree of  drying  out  is  not  uniform  throughout  the  soil.  It 
is  only  in  the  topmost  layers  that  the  process  may  extend 
to  such  a  degree  that  the  moisture  film  is  reduced  to  a 
minimum  for  capillary  movement.   As  the  {tS/ff/ffo- capillary 
point  is  approached,  the  upward  movement  becomes  more  and 
more  sluggish,  and  it  is  very  difficult  to  reduce  the  low- 
er soil  layers  below  this  point  even  though  the  upper  lay- 
ers may  have  a  considerably  decreased  moisture  content.  To 
stop  this  upward  movement  and  thereby  the  surface  evapora- 
tion is  a  chief  consideration  in  irrigation  farming  where 
water  economy  is  a  vital  factor. 

The  nature  of  the  soil  is  of  considerable  impor- 
tance.  The  finer  the  texture  of  the  soil  the  more  rapidly 
will  be  the  upward  movement  of  the  moisture  to  be  changed 


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69 


Into  vapour.   The  darker  the  colour,  the  more  heat  it  ab- 
sorbs and  hence  the  greater  the  evaporation.   The  richer 
the  soil  is  in  soluble  salts,  the  slower  is  the  evapora- 
tion of  water  into  the  air. 

Of  the  meteorological  factors,  the  evaporation 
is  most  largely  influenced  by  the  temperature,  sunshine, 
relative  humidity,  wind  and  rainfall.   The  higher  the  tem- 
perature, the  more  rapid  is  the  conversion  of  water  into 
v/ater  vapor.  Much  more  water  is  lost  from  a  wet  soil  on  a 
sunny  day  than  on  a  cloudy  day.   The  drier  the  air,  the 
more  rapidly  will  the  air  take  up  water  vapour.   Winds, 
likewise,  exert  a  strong  drying  efi'ect  on  soils,  especial- 
ly in  the  case  of  relatively  dry  wind.   It  has  also  been 
shown  that  the  wetter  the  soil  is  st  the  surface  the  more 
rapidly  will  be  the  water  evaporated  therefrom.   The  evap- 
oration of  water  from  a  soil  varies  as  the  initial  percen- 
tage of  the  soil  moisture. 

The  results  of  the  observations  at  six  stations  at 
which  evaporation  experiments  were  conducted  under  Dr.  For- 
tler  are  shown  in  Tables  XVI  and  XVII.   The  saving  by  cul- 
tivation is  also  clearly  shown  in  Figure  IX. 


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72 


The  process  is  not  difficult  to  understand. 
Water  moving  toward  the  soil  surface  must  pass  from  parti- 
cle to  particle  through  1iie  various  films  at  the  points  of 
contact  of  the  soil  particles.   The  smaller  or  the  fewer 
these  points  of  contact,  the  more  difficult  will  be  the  up- 
ward movement  of  the  water.   When  the  top  soil  is  loosened, 
the  points  of  contact  between  the  loose  soil  above  and  the 
compacted  soil  below  become  reduced,  and  hence  the  ascend- 
ing water  finds  it  difficult  to  pass  through  the  fewer 
points  of  contact.   The  more  thorough  the  cultivation,  or 
the  fewer  the  points  of  contact,  the  more  difficult  will  be 
the  upward  movement  and  the  greater  will  be  the  reduction 
in  evaporation  losses.   It  therefore  follows  that  the  deeper 
the  mulch,  a  greater  saving  can  be  expected.   That  this  is 
the  case  is  shown  by  Table  XVIII  which  shows  the  average 
losses  by  evaporation  from  a  free  water  surface  and  from 
tanks  with  mulches  of  different  depths  at  five  different 
stations. 


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llb  svi'l  Je    aa'*q?I>  Jno'isllii)  'io   a  ado  I  urn  d^Zw  aatrtad1 


73 


TABLE  XVI 1 1 / 


Period 

. 

Days 

i 
Loss  from   ' 

LOSS  froir 

[  Soil 

1  No 

'Mulch 
i 

3" 

Mulch 

5  " 

Mulch 

I  g  II 

Mulch 

Inches      'Pounds 

Pounds 

Pounds 

Pounds 

First 

3 

r~         i 

.86     '   9.6 

i 

1.9 

.48 

.48 

Second 

4 

.95     '   5.1 
i 

2.1 

.56 

.56 

Third 

3  ' 

.87     '  3.7 
r           i 

1.6 

.63 

.25 

Fourth 

4 

.95     '  3.6 
r           i 

2.3 

*   .89 

.43 

Fifth 

3 

.97     '  2.3 

i 

1.5 

1.08 

.  53 

Sixth 

4 

.99     '   3.1 
i 

2.4 

1.73 

1.07 

Total 

21 

r           i 
5.59     '  27.4 

11.8 

5.37 

3.32 

Equiva- 
lent 
loss  in 
inches 

t 
i 

'   1.75 

t 

.75 

.34 

.22 

ffable  XVIII  and  Figure  X  show  that  from  an  open 
unmulched  soil  surface  for  a  period  of  three  weeks  the  aver- 
age loss  was  27.4  pounds,  which  is  equivalent  to  1.75  inches 
of  water.   The  percentage  saved  from  each  depth  is  shown  in 
Table  XIX. 


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.XIX  s. 


74 


TABLE  XIX  (9j 


Condition  of  Sod 

Evaporation  loss 

Percent  of  saving 
on  evaporation  from 
unmulched  soil 

~^ 

Inches 

Percent  of  wa- 
ter applied 

No  mulch 

1.75 

29.2 

00— 

3"  mulch 

.75 

12.5 

57.0 

6"  mulch 

.34 

5.7 

81.0 

9"  mulch 

.22 

3.65 

87.5 

The  saving  therefore  of  a  six  inch  mulch  and  a  nine  inch 
mulch  varies  but  little  and  it  is  questionable  whether  it 
is  .economical  to  go  beyond  the  six  inch  depth. 

In  localities  where  the  available  water  supply  is 
limited  and  where  the  duty  of  water  is  high,  conditions  have 
forced  the  irrigator  to  resort  to  methods  of  irrigation 
which  will  result  in  a  lesser  waste  of  water  than  that  of 
flooding  the  entire  surface.   In  orchard  irrigation  expeci- 
ally,  but  also  very  extensively  in  all  crops  that  are  grown 
in  rows,  furrow  irrigation  has  been  largely  adapted.   The 
present  tendency  is  to  use  deeper  furrows  than  formerly 
used.   The  reason  of  this  practice  is  not  far  to  seek,  in 
that  it  is  quite  evident  that  under  such  conditions  a  smal- 
ler percentage  of  moisture  will  rise  by  capillarity  to  the 

surface  to  be  evaporated. 


I 


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75 


Tables  XX  and  XXI  give  the  result  of  the  exper- 
iments conducted  by  Dr.  Fortier  to  determine  the  saving 
of  water  by  various  depths  of  furrows.   The  tanks  receiv- 
ed a  six  inch  depth  of  irrigation  water,  followed  by  a 
six  inch  mulch  as  soon  as  the  soil  could  receive  it.   The 
results  are  illustrated  in  Figure  XI. 


- 


rloni  xie 


76 


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77 


TABLE  XXI  fr) 


i 

T 

i 

Loss 

'Amount 

sav- 

'Amount  sav- 

'Amount  sav- 

'Amount 

by 

'ed  over 

'ed  over 

'ed  over 

'saved 

evapo- 

'free water 

'flooded 

'surface  ir- 

'over 

ration 

'surface 

'surface 

'rigated 

'surface 

' 

t 

i 

'with 

'irrigat- 

i 

' 

'3"  furrows 

'ed 

t 

i 

' 

'6  "furrows 

Inohe  s 

'Inches  ' 

Per- 

'Inches 

Per- 

rlnche s 

Per- 

'ifiches "Per- 

i      i 

cent 

t 

cent 

t 

cent 

1      'cent 

(      i 

"T 

T~ 

i      i 

Water 

i      i 

1 

1 

i      i 

surface 

10.46 

t      i 

—  — 

1 

_  _ 

i    _  _ 

_  _ 

—  «    MV 

i      t 

1 

1 

i      i 

Flooding 

1.25 

'  9.21  ' 

88.0 

t 

__ 

_  _ 

_  _ 

i      i 

3 

Inch 

i 

1 

1 

i      i 

furrows 

.98 

'  9.48 

90.6 

'    .27 

21.6 

1 

<—  — 

i      t 

G 

Inch 

i       i 

' 

t 

i      i 

furrows 

.86 

1  9.60  ' 

91,8 

'    .39 

31.2 

.12 

12.2 

i      t 

y 

Inch 

1       t 

i 

1 

i      t 

furrows 

.72 

•  9.74  ' 

!           t 

93.0 

.  53 
i 

42.4 

'   .26 

26.5 

'   .14  '16.3 
i       i 

-VBS 


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75 

78 


Percolation.   Of  all  the  losses  in  the  applica- 
tion of  water  to  the  land,  deep  percolation  generally  ac- 
counts for  the  greatest  portion.   As  stated  'before  the 
probable  loss  by  deep  percolation  is  generally  from  twen- 
ty to  fifty  percent  of  the  water  applied. 

As  shown  by  Table  XIV  diagrams  of  the  moisture  de- 
terminations on  the  alfalfa  experiments  at  Davis  farm, given 
previously,  for  the  various  irrigations  fifty-seven,  seventy- 
four,  and  fifty-four  percent  of  the  water  applied  percolated 

1£;G£      5.52      6.60   '.  06 -.1 

below  the  first  six  feet  with  an  average  of  68.8  percent. 

Table  XXII  has  been  compiled  for  the  various  soils 

on  which  the  alfalfa  experiments  were  conducted,  showing 

2.20      5.23 
the  loss  by  deep  percolation. 


.1    398G01    9do     113    10        • 

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8.63  lo   asaw  ^  ridiw'  *aal  xia   *Ball   adJ 


silos 

no 


79 


TABLE  XXII 


i 

Class  of 

Average 

Quantity 

'Quantity 

'Percent- 

Loss  due  to 

Soil 

depth  ap- 

retained 

'of  water 

'age  re- 

deep  perco- 

plied per 

by  upper 

'retained 

'tained 

lation  be- 

irrigation 

six  feet 

'including 

'including 

low  six 

of  sod 

'probable 

'probable 

foot  limit 

'evapora- 

'evapora- 

Percent 

'i 

tion 

'tion 

'losses 

"losses 

i 

Silt  loam 

i 

t 

with  sandy 

i 

' 

loam  sub- 

i 

i 

soil 

15.02 

5.52 

6.60 

'   45.9 

56.1 

i 

i 

Silt  loam 

12.81 

4.24 

1   5.52 

1  41.5 

58.5 

i 

i 

Clay  loam 

8.78 

5.50 

1    4.56 
i 

•'  52.0 

I 

48.0 

Clay 

4.72 

" 

2.20 

1   5.28 

'   69.4 

30.6 

i 

i 

Very  heavy 

i 

Clay 

3.67 

1.06 

1    2.14 

58.5 

41.7 

i 

As  was  to  be  expected  the  results  show  that  the 
percolation  losses  were  rather  heavier  on  the  lighter  silt 
loam  soils  than  on  the  clay  soils.   Percolation  may  be  look- 
ed upon  as  capillary  movement  of  water  aided  by 'gravity,  and 
since  any  capillary  movement  is  dependent  on  the  texture  of 
the  soil,  so  too  is  the  rate  of  percolation  to  a  large  ex- 
tent proportionate  to  the  texture  of  the  soil.   Measurements 
have  been  made  which  show  an  absorption  on  blow  sand  soils 


ev 


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.alioe 
lo  d-nsacyom  -fxalllqao   a,/3  aoqi; 

lo  -rsmtfxatf   oilt  no   J-nasnaqab  ai  *«effleyoi^;^«»i-i'lq«o  Ti"^  ao 
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80 


of  as  much  as  twelve  feet  of  depth  of  water  in  twenty- 
four  hours.   On  the  other  hand  it  has  been  found  that  in 
the  case  of  a  well  dug  in  heavy  clay  in  the  Sacramento 
Valley,  the  water  had  not  yet  percolated  twelve  inches 
laterally  in  a  week's  time.   The  general  rates  of  perco- 
lation to  be  expected  in  depth-  of  water  in  foot  per 
twenty-f  our  hours  {Mm/fay} 

Ledium  heavy  soils  1  foot 

Clay  loams         2  feet 

Loam  3   " 

Sandy  soils        5   " 

With  light  soils  it  is  difficult  to  cover  the  surface  suf- 
ficiently quickly  so  that  no  part  will  absorb  more  than 
can  be  retained;  with  heavy  soils  the  difficulty  is  to  se- 
cure full  absorption  of  the  water  to  the  required  depth. 

It  follows  therefore  that  where  for  instance  for 
alfalfa  on  a  sandy  loam  the  best  practice  would  require 
four  to  seven  and  one-half  inches  irrigations  (assuming  a 
maximum  beneficial  seasonal  use  of  thirty  inches),  it 
would  be  best  to  apply  eight  to  three  and  three- fourths  ir- 
rigations in  the  case  of  sandy  soil  and  clay  soils, --in  the 
first  case  to  prevent  deep  percolation  loss,  in  the  second 


Jool  1    silos   ^vs9x; 


•  lye   soeliua   odd"  TOVCO  ot  tfljcroJtllI&   2! 
fi.t   eioin  fHcecfs   11/w  d'lf      on  if  s rid" 


— BS    O  -!    t;  X    Y"^ 

.riitqssb  ks-Yhjpot   etitf  o.t   ti'd-sw  9£&   lo   / 
iol  ^onJSJartJt  lo'i 


81 


to  secure  full  absorption.   The  most  common  method  of  ap- 

: j.   .:r  1;-  etui  be 

plying  the  water  to  the  land  is  by  spreading  it  over  a 
slightly  sloping  surface.   Under  such  conditions  the  dis- 
tribution of  the  water  should  theoretically,  be  somewhat 

'--s'l  '-  -  -'-'•-.  /-.  r 

as  shown  in  Figure  XII. 

lie  area  Hfi«  C«  D,  Hi  D. 
The  depth  of  initial  absorption  efba  represents 

the  minimum  depth  of  irrigation  with  which  the  land  can  be 
covered  under  any  conditions.   As  the  water  travels  over 
the  check,  the  depth  of  absorption  from  the  flowing  stream 
will  be  proportional  to  the  time  during  which  each  part  of 
the  check  is  covered,  being  greatest  at  the  upper  end,  as 
shown  by  fgb — gb  being  somewhat  concave  upward  as  the  water 
will  travel  more  rapidly  at  the  upper  end.  When  the  water 

•  '-   '  *  •-"  T    .-   •>•£     ft  01X^3     •'.  vch 

has  reached  the  lower  end  or  often  somewhat  before  it  has 
reached  the  end,  the  supply  is  shut  off.  For  a  short  period 
all  of  the  area  would  be  covered  and  absorption  takes  place 
uniformly  over  the  whole  check-  as  shown  by  chcb.   Gradually 
however  the  upper  end  will  become  unwatered  and  the  water  on 
the  check  will  recede  toward  the  lower  end,  the  absorption 
being  greatest  at  the  lower  end  where  the  water  remains  the 
longest  as  represented  by  hdc.   The  total  depth  at  the  top  of 
the  check  will  hence  be  eh  and  will  necessarily  be  a  function 
of  the  length  of  the  check  or  ea.   If  therefore  it  should  oc- 


.    2  od 
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82 


cur  that  at  the  head  of  the  check  water  is  lost  by  deep 
percolation,  this  can  be  considerably  diminished  by  divid- 
ing the  check  into  a  number  of  subsections,  obtaining  a  dis- 
tribution as  on  Figure  XIII.   The  dotted  lines  shows  the 
distribution  with  an  undivided  check.   The  saving  in  water 
is  therefore  represented  by  the  area  HHu  Dn  Dt  Hi  D. 

Don.  H.  Bark  has  conducted  extended  experiments 
illustrating  these  relations. 

An  experiment  was  conducted  on  a  strip  of  clover 
45.9  feet  wide  and  2559  feet  long.   The  strip  was  divided 
into  seven  equal  divisions  337  feet  long  and  a  head  of  ap- 
proximately three  cusecs  was  turned  into  the  upper  end  of 
the  strip.   The  head  was  held  constant  and  the  length  of 
time  that  was  required  for  the  water  to  advance  across  each 
successive  division  as  the  stream  advanced  down  the  border 
check  was  noted.   The  results  in  Table  XXIII  were  obtained. 


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85 


TABI£  XXII I 


Division 
number 

Length 
of  run 
feet 

• 

Irrigated 
area 
acres 

- 
Time  required 

~r~ 

Acre    'Average 
feet    'depth 
Applied  'in  feet 

Hours 

Minutes 

1 

537 

.38 

1 

7 

i 

.28  '   .73 
i 

1--2 

674 

.77 

2 

30 

.63  '   .82 

1--3 

1011 

1.15 

4 

00 

1.01  '   .88 

1 

1--4 

1348 

1.55 

5 

40 

1.43  '   .93 
i 

1--5 

1685 

. 

1.92 

8 

25 

2.12  '  1.11 
t 

1--6 

2022 

2.30 

11 

30 

2.90  '  1.26 
i 

1--7 

2559 

2.68  '   15 
i 

40 

3.95  '  1.47 

i 

The  Table  shows  clearly  that  the  amount  of  water  that  is 
required  for  the  irrigation  of  gravelly  soils  increases 
greatly  with  the  distance  over  which  the  water  is  flood- 
ed.  Had  this  strip  been  divided  into  seven  sections  by 
the  construction  of  six  cross  ditches,  the  time  required 
would  have  been  only  seven  times  as  long  as  that  required 
by  the  first  strip,  or  only  seven  hours  and  forty-nine 
minutes,  as  compared  to  the  fifteen  hours  and  forty  min- 
utes that  were  required.   Also  an  average  depth  of  applica- 
tion of  only  .733  feet  would  have  been  required  as  against 
the  1.47  feet  which  were  required  when  it  was  flooded  the 


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entire  length  of  the  2359  foot  border.   A  total  saving 

of  fifty  percent  in  the  time  water  used  would  have  re- 

''AC'ce  i'^et  of     'Correspond in- 
sulted.  The  results  emphasize  the  fact  that  the  econom- 
ical irrigation  of  especially  porous  soils  can  only  be 
effected  by  flooding  comparatively  short  distances  at  a 
time. 

The  effect  of  varying  the  size  of  head  was  in- 
vestigated by  the  United  States  Reclamation  Service  in 
1910  and  1911.   The  curves  in  Figure  XIV  show  the  rela- 
tion between  the  number  of  acre  feet  on  the  tract  and  ' 
the  duration  of  the  irrigation,  which  depends  on  the  head 
of  water  used. 

Table  XXIV  has  been  compiled  for  Kingsbury  Tract 

No.  8,  assuming  various  times  in  which  the  irrigation  was 
••.;•.?  a  tei»  o-jt.k  of  1  rr  '.••:•  I  c-n  "savr:-  UM-  acr€  •  nd 
to  take  place. 


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85 


TABLE 


Time 

Acre  feet  of 
water  registered 

i 

Corresponding 

head  in  cusecs 

i 

5 

2.60 

6.25 

8 

5.70 

5.60 

10 

16 
k 

4.0 

<  ';   V-  0'  *• 

4.5 

4.8 

• 
3.02 

20 

4.7 

2.85 

60 

5.9 

1.17 

The  results  show  that  decreasing  the  size  of  irrigation 
head,  causes  a  proportionately  larger  increase  in  the  time 
necessary  to  obtain  a  complete  irrigation,  and  therefore 
requires  a  greater  depth  of  irrigation  water  per  acre  and 
a  greater  loss  by  deep  percolation. 

The  degree  to  which  these  principles  have  been 
adopted  in  practice  is  shown  to  some  extent  by  the  follow- 
ing.  Usually  checks  vary  from  three  hundred  thirty  to 
thirteen  hundred  twenty  feet  in  length,  six  hundred  sixty 
being  typical  for  medium  soils.   The  width  of  the  check  is 
adjusted  to  the  soil,  slope  and  size  of  irrigating  head. 

The  r.idths  vary  from  thirty  to  one  hundred  feet  for  differ 

?? 
ent  slopes  and  sizes  of  head,  the  ~  .arrow er  checks  being 


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^looci?5C!  Q'psb  "^cf  seol 
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86 


used  on  steeper  slopes  with  smaller  head.   Checks  66  x 
660  contain  one  acre  and  are  typical  of  the  practice  under 
conditions  suited  to  border  irrigation.   The  size  of  the 
stream  varies  from  about  .02  to  .15  cusec  per  foot  width 
of  check  or  from  two  to  ten  cusecs,--the  most  usual  condi- 
tions being  .08  to  .10  cusec  per  foot  width  of  check.   The 
slopes  to  which  this  method  is  best  adapted  varies  from  two 
inches  to  one  foot  per  hundred  feet,  slopes  of  four  to  six 
inches  being  the  most  usual. 

In  furrow  irrigation  it  is  difficult  to  obtain 
a  uniform  application  throughout  the  length  of  the  furrow. 
The  best  method  to  obtain  a  fairly  uniform  distribution  is 
to  either  reduce  the  total  length  of  the  furrow,  or  to  in- 
crease the  length  of  the  furrov/s  in  the  lower  portions  of 
the  fields  by  zigzagging  them  in  orchards  or  building  small 
basins  for  ponding  purposes.   The  size  of  the  furrows  can  be 
adjusted  to  the  slope  and  head  in  each  furrow,  in  light 
soils  using  as  large  furrov/s  and  heads  as  will  not  cause 
erosion;  on  heavy  soils,  smaller  and  longer  furrov/s  with 
corresponding  longer  "sets"  should  be  used. 

The  lateral  percolation  in  furrov/s  has  been  ex- 
tensively studied  by  Dr.  Loughridge.   The  water  applied  moves 
not  only  vertically  downward,  but  in  every  direction  from  the 


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87 


wetted  furrow.   The  downward  movement,  aided  by  gravity, 
will  be  the  most  rapid,  diminishing  as  it  becomes  more  and 
more  horizontal.   This  is  very  clearly  brought  out  by  the 
experiments  of  Dr.  Loughridge  and  McLaughlin,  quoted  pre- 
viously. 


TABLE 

Water  removed  from  tanks  'by  days  expressed  in 
percentages  of  amount  in  thirty  days. 


Days 

1 

Decomposed 
light  san- 
dy soil 
20 

Loam 
31 

,  .,  f  ,. 

'  Heavy 
'  clay 

loam 

i 

Sand  and 
gravel 
wash 
70 

Heavy 
lava 
ash 
90 

1 

17 

22 

i 

'   26 
t 

18 

17 

3 

30 

36 

1   42 
i 

30 

29 

5 

38 

42 

'   51 

i 

36 

37 

10 

53 

58 

1   67 

52 

53 

t 

15 

67 

70 

'    78 
i 

64 

67 

20 

81 

81 

1   86 

79 

81 

30 

100 

100 

1   100 
i 

100 

100 

Table  XXV  shows  the  great  uae  of  water  during  the 
first  days  of  the  experiment.   In  all  cases  more  than  one- 
half  the  total  quantity  of  water  used  in  thirty  days  was 
used  in  the  first  ten  days  or  one- third  of  the  time.   The 


(• 


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ssstqx©  3Y*&  ^c:  a^iti^d-  mo'il  & 

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» 
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I                     r-i  ri 

VI 

»           Si        '         82        '         22 
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vs 

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88 


lighter  the  soil  the  smaller  the  relative  percentage  of 
water  used  during  the  first  days,  and  the  heavier  the  soil 
the  greater  the  relative  use  of  water  during  the  first  few 
days. 

Figure  XV  from  the  experiments  of  LicLaughlin 
shows  thattiae  heavier  the  soil  the  less  extended  will  be  the 
wetted  area  with  the  lapse  of  time.   Therefore,  a  light  soil 
will  "sub"  much  farther  in  a  horizontal  direction  than  a 
heavy  soil. 

The  law  of  lateral  distribution  of  the  moisture  is 
in  general  of  the  same  nature  as  for  downward  movement  i.  e. 
the  water  will  tend  to  distribute  itself  inversely  with  the 
distance  of  the  soil  particle  from  the  source  of  supply. 


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89 


TABLE 
Distribution  of  moisture  in  horizontal  flumes 


Light  sandy 
soil 

Loam     'Heavy  clay 
'loam 

Heavy  lava  ash 

Dis- 
tance 
Inches 

Average 
percent 
of 
moisture 

Dis- 
trict 

Average  'Dis- 
'trict 

i 

Average 

Dis- 
trict 

Average 

3 

f—  —      ~ 
24.38 

f* 

9 

22.85    3 

44.58 

5 

31.07 

9 

20.85 

22 

23.10  '  12 

43.61 

9 

28.85 

i 

21 

20.81 

34 

21.25  '  34 

40.49   18 

27.21 

45 

18.22 

52 

19.50 

30 

39.43   30 

26.40 

69 

16.70 

64 

15.85 

33 

[ 

36  .  33   42 

25.57 

81 

14.24 

'  54 

25.47 

i; 

ti 

i 

93  " 

14.18 

• 

'  72 

20.49 

1 

105 

12.36 

'.       '  84 

22.57 

i 

111 

10.54 

1  96 

19.20 

•»u 

i 

117   '  7.56 

•  i 

i 

i:-  •'       i 

Observations  on  medium  heavy  soils  in  the  Sunny- 
side  project  indicate  that  by  six  days  after  irrigation  the 
moisture  will  be  relatively  uniform  across  furrow  spacings 
as  wide  as  six  feet  where  water  had  run  in  the  furrows  for 
twenty-four  hours.   It  was  also  found  that  fairly  uniform 
moisture  distribution  was  secured  within  forty- eight  hours 
after  irrigation  with  twelve  hour  sets  on  four  feet  furrow 
spacings.   With  sandy  soils  without  heavy  subsoils  where  the 


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furrow  spacing  exceeded  three  feet  heavy  downward  move- 
ments occurred  before  the  moisture  met  laterally  between 
furrows  with  heavy  subsoils  at  depths  of  from  four  feet. 
Pour  feet  spacing  of  furrows  gave  good  results.   The  trend 
of  practice  is  in  favour  of  a  smaller  number  of  furrows  of 
greater  depth,  in  which  small  streams  of  water  are  permitted 
to  run  fifty  to  seventy  hours.   This  increase  in  the  "sets" 
has  not  increased  the  total  quantity  applied  in  any  one 
season  for  there  has  been  a  corresponding  decrease  in  the 
number  of  irrigations.   This  method  not  only  reduces  the 
amount  of  moisture  lost  through  evaporation  by  upward  capil- 
lary movement,  but  also  distributes  the  water  in  the  subsoil 
more  evenly  and  produces  a  greater  sideway  absorption.   It 
also  tends  to  produce  a  deeper  root  system  in  the  crops. 

The  size  of  head  or  the  flow  turned  into  each  fur- 
row should  be  adjusted  to  the  soil,  slope  and  length  of  run 
--as  pointed  out  previously.   The  best  results  are  secured 
by  using  larger  heads  until  the  stream  has  worked  through  to 
near  the  end  of  the  furrow  and  then  reducing  the  amount  in 
order  to  prevent  excessive  waste. 

The  size  of  the  stream  used  In  each  furrow  is  most 
conveniently  expressed  by  giving  the  number  of  furrows  which 
would  be  set  with  a  flow  of  one  cusec.  On  heavy  soils  one 


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ni  ctnwoKto   9fi^.  ^niowbst  na/f*.  bxis  -woiiiA ' ed*''  lo  bn; 

evxasscxs  *-KDV9riq  od- 
:Ja    SJEtd"  lo   ss.ta   9ffT 
LmY  a'aroiTirl  lc  i  2rlo"  T^nxvis         b9JG9-:ciX9  Y     P9 


i  woitt/i  rioes  ni 


Q   blwow. 


91 


hundred  to  one  hundred  fifty  furrows  per  cusec  are  often 
used.   On  the  heaviest  types  which  absorb  water  slowly, 
two  hundred  furrows  per  cusec  are  not  unusual  and  on 
steep  slopes  this  may  reach  five  hundred  in  extreme  cases. 
On  sandy  soil  the  head  used  per  furrow  is  generally  l/ioo 
Where  the  slope  is  flat  larger  heads  are  preferable, 
1/60  cusec  being  an  average. 

Surface  Waste.   This  loss  is  largely  dependent  on 
the  skill  and  care  taken  in  the  preparation  of  the  land  for 
irrigation  and  in  the  application  of  the  water.   The  run» 
off  collects  in  hollows  or  cuts  channels  to  connect  it  with 
the  larger  bodies  of  surface  water.   When  water  is  applied 
by  the  flooding  method,  it  is  relatively  easy  to  control 
the  run- off  by  building  levees  around  the  field-- as  in  the 
Border  and  Check  methods.   In  such  cases  the  waste  should 
be  negligible  in  amount.   Flooding  methods  will  on  an  aver- 
age give  a  ten  percent  waste  and  furrow  irrigation,  due  to 
the  greater  difficulty  in  obtaining  a  uniform  distribution, 
will  generally  have  a  somewhat  larger  waste.   In  any  case, 
the  run-off  water  should  be  carefully  and  skilfully  used  on 
lower  fields.   The  problem  is  one  which  must  be  solved  on 
its  merits  on  each  individual  farm.   No  general  rules  can 
be  laid  down  for  using  the  run-off,  as  necessarily  this  use 


etfo  uq  awoiiirl  ^dlil  baribnuri  ano  od"  bsibru/rf 
svr  d-'ioads  rielxlw  aoq^d   craolvssil  sild  x$0      .bsai; 
no  bus   XawaucuJ  don  913    osawo  ii»q  awoiml  b9rtbm;ri  owd 


n 


avll  r£ofle«x 

ol  190  bsaw  6as:i_  ^i»  Iloa 
;h:ll   ai   oqols 


no  *«ei«i9q8l>  ^1981-^1   ai   a 

iol  bn^X   sii^  lc  noWaieqs  ic»   a.:     nl  n?^j   O'IBO  brw   lliila  arid" 

.i9d-3» 

d-os:-noo   od    .ji  onnoiio   atuo  10   awoXXoii  nl   E^osIIoo   llo 
al  isd-flvr  riari.?      .i9*fiw  ooBl-i.ua   lo   aslbcd  1331  oX   sitt 
od  '^aso  ^XsvWaXsi   al   31    tboxi*s:s  gnibooXl   3a"  ^d' 
9itf   rxi   BB~5X9n   9^^  bfOfoi/i    assvsl   gitibXlud  X^  He  -run 
bXi/oi-ia   sctajBw.Siid-   asaao  aowc    nl      .sboil 

-isvB  iiiJ  no   jiiv,'  eborid-sm  ^ixbooXfi     ,.;t£iuoaia  n±   eXdlglXaen  9-J 
od-   ajoi)  .aoWasli'J'J:   woiii*1!  bns   9cJ-SJ3w  dnsoisq  nsJ-   s   9vl3  333 
,Hoi*.wdIiJalI)  raio^lfliJ  a  gnlnlsddo  r;x  ^Xuol"il.t5  .19-0913 
tes£0  Y«£  ^      -siaaw  lagi^X  iariwge^os  a  averf  ^llBiinss   - 
no  bsajj  ^iii/iiiaia  5«a  ^XXi/A9ieo  3d  bXuorla  isd'sw  llo-nui  sad- 
no  bsvXoa  9d  *auffi_dol£iff  ano  al  B»Xdoiq  9ifi      .abXsil  iswol 
TJ_>~    ^aryri  ij3i3n9H  oil 


92 


will  depend  largely  on  the  layout  of  the  individual  farms. 
Table  XXVII  shows  the  average  waste  from  fields  at  Billings, 
Montana,  for  different  crops  and  soils  in  percent  of  total 
water  received. 

TABLE  XXVII 

Average  waste  from  fields  under  different  crops  at 
Billings,  Montana.  ( Harding )/2/J 


Crop 

Heavy  Soil 

I            i 
Medium  Soil  'Ligh  Soil    '  All  Soils 

No.  of  'Mean 
obser-  'per- 
va  ti  ore'  cent  - 
'age 
'of 

'waste 
i 

No.  of  'Mean  'No.  of 
obser-  'per-  'obser- 
vations'cent-  'vations 
'age 

'of 

'waste  ' 
t 

Mean 
per- 
cent- 
age 
of 
waste 

II  o.  of  rMean 
obser-  'per- 
vatione'cent- 
'age 
'of 

'waste 
i 

Alfalfa 
Grain 

Cultivated 
Crop 

56   '   19 

*      \ 

15   '   15 
i 
• 

13   i   20 
t 

78 

36 

20 

i 

4.5  '   20 

! 

5.5  '   11 
i 

i 

.6  '    6 
t 

5.7 
14.3 

9.2 

i 

154   '  10 
i 

62   '9.4 
i 

! 

39   '8.  5 

Mean  for 

all 

. 

i 
i 

84    18.5 

134 

! 
J 

4.5  '   37 
t 

9.0 

i 

i 

255   '9.7 
i 

.    llIJ 
Iscto; 


no  yLaaizI.   bnoqsu  III* 

B  sMsi'l  noil  9^  saw  93313  vs   orfcJ    aworla    IIVXX 
staaoisq.  nl  alioa  brtB  aqoio  tasisllib  10  1 


IIVXX 


cfs  accio  driSisTlilb 


ablsil  moil  aisaw 


—  —  ..   ,--*—  .-  —  —  -  •  '-•:  -•••*,.                                                                    1 

-r^-j              '                    fff,  f^1    lice.  r.u/i£>8fcl 

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-^neo'snoid-Bv1  -cfaso'ancid-.sv'  -^nso'aioloBv 

loi     •              •  .ip  'i 

3daBW                   ocrasv,'                   SJas 
:                   '                                                    ' 

nsasl'    ic.ollv 

—  13fl      —  "i' 

—  ctrioo  ctici'JijV 

'   ,  !                                1 

IO 

1 

SCfSBW 

, 

-    i       AO      i    r    \   !      QV      !    .D  i       i      gg                 airl-slXA 
01          £31   !    ^.^                        o»*                                                  , 

i  .                  '                 !                                      j                                                                                          ^ 

k  S1       So      '     S.-M'       11      '     S.S    '       55      ' 
i                 i                                              i                 ;              j 

•e.s;     es    '   &,«  :      >      ;    a.     ;     oa    ;   02    j     si    ;  "  -     *«o 

,               ,             !               !             i                i             '                '         io1  asaM 

'j     1                         r      *               IT'             '                       V       !                 \S"   r        '    f>       ft  f        '                -«!^i             '                                                 LS.& 

V.6                      y-«*    .       v^      ,    «•*   ,       ^    ^'0*    ,                 , 

93 


CHAPTER  VII 
THE  FERTILITY  OP  THE  SOIL     »*•• 

It  is  often  taken  for  granted  that  irrigated 
lands  do  not  require  any  artificial  fertilizer  because  of 
the  fact  that  the  water  itself  furnishes  the  required 
fertility.   While  a  good  irrigation  system  does  have  great 
advantages  and  while  the  silty  waters  used  in  irrigation 
frequently  carry  valuable  fertilizing  material  (See  Table 
XXVIII),  dependence  for  maintaining  and  increasing  the  fer- 
tility of  arid  lands  cannot  be  placed  wholly  upon  the  ap- 
plied irrigation  water. 

TABLE  XXVIII 

Showing  the  amount  of  fertilizing  silts  in  various  rivers 

of  the  U.S.A.  (Etcheverry) 


River 

'Pounds  of  Pot- 
ash per  acre 
foot  of  water 

Pounds  of  Phos- 
phoric acid  per 
acre  foot  of 
water 

Pounds  of  Nitro- 
gen per  acre 
foot  of  water 

Rio  Grande 
Salt  River 

Colorado 
River 

325.5 
265, 

16.34--444.60 

31.4 
10.5 

2.26  —  43.56 

24.4 
9 

1.03--69.7 

I1V  /ii 


•Jios 


YTLHTHSS:  SET 


rxci 


lo  se-aeoscf  riesill;t'i3l 
-s  grief   aaj-i^ 
avsri  asc.b  nsd-3'is  n 
ai  fjo 


nectio   si   tfl 
eii^pe-i  ctcm  o£> 


-qs 


noqw  ^liorf?/  £>90iilq  sc 


'ri      oc§   a   sii^lV      .^J 
^ctlle   siid"   sli^w  arus 


rio'l 


abnsi 


t(IIIVXX 


lo 


IIIVXX 

>i  auoirfav  rxi  a^Iis  gnisilx 

.A.  2.0    9iut    10 


lo 


oittfi  srl* 


-o'; 


_T_ 

1   ajjfijjo'i  '  -aorf'i   Ic    sbiiijoi 
isq  n©§'  T3a  fjioa   ol'ioilq 

10    d-OOl'          "lo    J-QOl    3--I0.8 

-loi   lo   abrtwoi 
3-10.3  isq  riss 
•iscfflv/  lo  ctool 

«TM 

8                            5  .  OX 
i 

-SO.f     '             Ar>.^.A__AQ     Q 

s.ass 

s^iasiO  oiH 
lavifi  ctlaS 

94 


Even  in  Egypt,  where  the  Kile  sediment  has  a  high  fertil- 
izing capacity,  it  lias  been  found  that  manure  and  artifi- 
cial fertilizers  should  be  used.   Sir  William  Willcocks 
in  his  "Egyptian  Irrigation"  says  £4-) 

"It  would  be  a  healthy  innovation,  indeed, 
if  the  provision  of  suitable  manures  were 
to  be  considered  as  an  essential  part  of 
the  project  for  providing  perennial  irri- 
gation.  The  day  is  not  distant,  I  believe, 
when  governments  which  provide  irrigation 
works  will  also  provide  manures,  and  sell 
the  water  and  manures  together,  one  being 
as  essential  as  the  other.   I  know  well, 
from  observation,  that  a  well  manured  field 
needs  only  half  the  water  that  a  poorly 
manured  field  does;  and  in  years  of  drought 
and  scarcity  manures  almost  take  the  plsce 
of  irrigation.   Why  should  there  not  be  a 
manure  rate  as  well  as  a  water  rate?" 

Organic  matter,  especially  when  it  lias  been  redu- 
ced to  the  form  of  humus,  has  a  great  capillary  capacity, 
far  excelling  in  this  regard  the  mineral  constituents  of 

the  soil.   Its  porosity  affords  an  enormous  internal  surface, 

\ 

while  its  colloids  exert  an  affinity  for  moisture  which 
raises  its  water  capacity  to  a  very  high  degree.   Its  tenden- 
cy to  swell  on  wetting  is  but  a  change  in  condition  when  ap- 
proaching its  maximum  moisture  content.   The  following  data, 
taken  from  Lyon  Pippin  and  Buckman,  give  an  idea  of  the  capil- 
lary capacity  of  the  soil  organic  matter. 


ni  n*v3 

liJ^iB  ftn.3   s'lirnam  d-B-ckt  brtwol  nasd   as:!  d  1    .  ^dloaqflo  gnlsl 
aaioeoIIlW  raallliW  il3      .beau  scf  bluorfo   artsailW'isl  leio 

3-33  "noi.l-BSiiil  ixaWq^-^a"   alii  nl 


,t-99l>nJt    .noi-favor^ii  ^dcfljssif  JB   scf  5Iuo-r  ctl" 
s^aw  as^jt/rtem  oicfsctiifu    lo  nolaivoiq  arid 
lo  d'l/sq  Ie-i.Jno2a9  rt.s   as   fisneblsncd   scf  od" 
laliine'xoq  ^rxlclvoiq  to' 
.tl)   .Ion   ul 
xiolrfw 

II  3  j  DIIJ:    «  a  giJjroiK  9ibl:vcriq  oale   IIlw  2ii 
eno    .ri9...'di9§od1   ae^i/iis 

\YO£Di  .-lOif-ic     8111    2G 

blsll  !>0rtJjjctBtr:  IIsw  a  daiid 

•^1  iooq  s   dsrict.  'i9j.f.%,v;  arid-    ilsd  vino 

^jfl^i-oif)  lo  'six:  9',:  rri  bun    jascri  blsll  b5fiUxaK. 

90-:Ia   sild-  aiiBd"   ^ccrrtls   ca^jmom  v^loisoa  bna 

B   sd  -ion  sister   oluorid   -j£T*J      .noWs^liil  lo 

CJ3    liO'.Y    2-3 


-9    2&&   tSimttJii-  lo  KPio'l  siiJ    od1 
lo   slnDi-'^l^anoo   Is'isijlci..  odd  biegs'i   alrlct  n±  jinlllsoxs  ^ul 

ijja   I.-iiriidr.'.!    siicftrrons  m;   cjbicTl^   Y^-soicq  ad"!      .I±oa   arlj- 

> 

doi^ivf  9t/-fd"aloisi  ic'i  ^diai'lls  JIB  tfiaxo  .abiol.loo  .a^J:  aliiiw 
ail  .ggisab  ilgM  ^xev  J3  oj  Y*^05"^0  isd-aw  aii  ^o^i^ 
v  noi  ibnoo  ni  a'snf^io  a  ctwo"  al  snid-iow  no  Ilawa  od-  ^o 


-Ilqao   9d*'  lo  a&bl  £W   avlg    ,nii.r4fojjQ  I      i';i 

.i^d-sm  oi.  3ii,f 


95 


Percentage  of  water 
Humous  extract  from  peat  1200 

Non-acid  extract  from  peat  645 

Vegetable  mold  509 

'  _'  '__  Peat  190 

Garden  loam  7$  humus  96 

Illinois  prairie  soil  57 

Field  loam  3.4$  humus  52 

1  61.0  . 

•Mountain  Valley  loam  1.2%  humus       47 

Even  after  allowance  has  been  made  for  an  in- 
creased hygroscopic  coefficient  due  to  an  increase  in  or- 

50  63.        !   S0._4        9£.7  -JL*  JLj&ljk*3£+ 

ganic  matter,  the  effect  of  the  latter  is  very  strongly 

marked  on  the  capillary  capacity  of  a  soil.   It  is  equally 

evident  that  with  a  well  manured  soil  there  will  as  a  con- 

:rr.c   reculr.fa    shavr  :'    F^-—"1 

sequence  be   a  marked  economy  in  the    amount   of  water  used 

to  procure  a  reasonable  crop. 

The  experiments  at  Utah  on  grain  and  stover  gave 
the  following  result s--an  average  of  six  years. 


••j&vq.  raoil   tfojBiJX9   awomi/ii 


eos  Mora 


(V  irasol 
IJtos    sitlBiq  alonllll 


-ul  na  rio'i   9bsai 

c         -9aa9-r.!>ol  na  ct    swb  .JnsloiTlsoo 

ai  i9Jda!   sxi^  lo   ^oori9   9^    «t8;ttBm 

no 


lo  ^loaq*o  - 

-rxoo   a  a*   ill*   9io,ut   lioa   b^-mam  Ii*w   a  rWlw  Jaile 
lo   cTnworffi    srli  ni  ^raoncss  Jos^a.Tt  a   scf 

.qo-io  aXcfanouaet  '3   siwooiq  od" 
'  no  dscTJ   --j   8-ja9fltil9<lX9   9rrr 

3'i  sotwo.IIol  9-W 


96 


TABLE 


Irri- 
gation 
ap- 
plied 

Grain 

~. 

.  Bushel 

s  per  A 

~T  ' 

ere      Stov 
i 

i 
i 

er  Tons 

per  Acre 

Inches 

No 
manure 

5  tons 

manure 

15  Tons 
manure 

Aver-  'No 

age   'manure 

i 

5  tons 

manure 

. 

15  tons  'Aver- 

manure  'age 
i 

Hone 
5 
10 
20 
30 

57.9 
61.0 
59.7 
67.6 
65.1 

73.3 

86.1 
83.0 
87.7 
90.4 

75.9 
91.4 
92.5 
99.1 
95.7 

i 

67.0'   2.11 

79.5'   2.32 
i 

78.4'   2.55 
t 

84  .  8  '   2  .  81 
i      i 

83.1'   2.86 

3.25 
3.77 

3.73 

~ 

4.04 
4.19 

t 

3.92  '3.09 
i 

4.48  '3.53 

4.25  '3.51 
i 

4.85  '3.90 
i 

4.77  '3.94 

1  63.9 
I. 

1™" 
83.8 

90.0 

79  .  2  '   2  .  88 

i 

4.07 

t 

4.50  '3.81 
t 

The  results  show  the  highest  yield  of  grain  with  a  twenty 
inch  irrigation  duty;  more  than  this  quantity  of  ?<ater  de- 
creased the  yield,  and  with  as  much  as  forty  inches  of  water 
there  was  slightly  less  grain  than  with  five  inches.  A  some- 
what higher  yield  of  stover  was  obtained  with  thirty  inches 
than  with  twenty  inches  of  water,  but  the  yield  was  decreased 
with  forty  inches.   The  average  of  six  years  shows  that  water 
applied  in  excess  of  twenty  inches  to  corn  was  not  only  wasted 
but  was  postively  injurious  to  the  yield  of  grain.   The  yield 
of  both  grain  and  stover  was  decidedly  increased  by  manure, 
the  stover  showing  the  effect  considerably  more  than  the  grain-. 


"T~ 

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-30 


lo 

•  Siiio'a  -'- 
aeiloni 


arW  woila   aj'lw&oi  adT 
v,.!«nJt  ifortl 

aasi  •; 
. 

sild"  d"wd    t'isd'av/  lo   asiioni 
awoua   a'laav  xia  lo   sgJisve   sifT      .8" 
d'on  ac»  irico   cd1   ssiionl  vd/ii^./d'   lo    uasoxa  nl 

*         u  _*•   ---    • 

bi8l^  siLJ   od'   aiJoliJL'^nl      •  svitaoq  as\7 

oso  a^Jw  i3vcd"d  tn  •  niJ3^3  rid'od  lo 
.3  .zUid-'anlwotia  i»vo 


97 


The  increase  was  much  greater  for  each  ton  of  manure  with 
the  five  ton  than  with  the  fifteen  ton  application. 

Most  of  the  soils  of  the  irrigated  regions  are 
deficient  on  humus  and  organic  matter,,  and  it  should  always 
be  the  first  object  to  supply  this  necessary  amount  of  fer- 
tilizer.  This  is  usually  done  by  the  growth  of  alfalfa, 
clover,  peas  or  some  other  legume,  turning  in  the  green  crop 
and  thus  putting  the  nitrogenous  matter  directly  into  the 
ground.   It  is  often  desirable  and  necessary  to  supplement 
this  by  some  form  of  fertilizer,  usually  the  ordinary  stable 
or  barnyard  manure. 

If  leguminous,  it  is  generally  grown  as  a  cover 
crop  during  the  non-irrigated  months  of  the  year.   Much  of 
the  success  of  this  method  is  dependent  on  the  skilfull 
handling  of  the  water  supply.   During  winter  months  the  cover 
crop  will  receive  all  the  necessary  water  from  the  rainfall, 
but  great  care  must  be  exercised  during  the  summer  months 
that  the  water  intended  for  the  main  crops  is  not  absorbed  by 
the  cover  crop  to  the  detriment  of  the  first.   In  some  lo- 
calities an  extra  amount  of  water  is  put  on  the  .land  especi- 
ally for  the  cover  crop, --being  in  addition  to  the  required 
amount  of  the  main  crops.   In  other  districts  again,  it  is 
the  practice,  to  apply  only  sufficient  water  for  the  main 
crops  and  to  let  the  cover  crops  care  for  themselves.   It  is 


rf*iv;  wnflm  lo  noa   dose  iol  *e*fl9iB  down  BOT  oaaeionl 
.nol*sollqqj8  no*  neatflil   srfd"   ii*lw  «afi*  no*   avll 
anoJb?*-!  had-asiTil   3*i*  1°   alloe   9ii*   to   *ioM 
a  Muoria   ^1  bns    ,-19.**  SKI  oinagio  b£i«   aj/nunl  no 
10  Jmroiaa  rx^aeodn  3l:W  ^Iqqwa   ocf   ^osLcfo   *a-ill 
«allallfl  lo  Jiiwoi3  silcr   Yd  snob  ^IlBysw  a±   sirTI      . 
qo-^o  «99t3  dto  nl  snlq;cu*    ,  9,-,-iuaeI   -leitto   s.uoa  ^xc   aaeq 

odnl  ^l  B-.t  a-o-oneo^in  sitt  snld*i/q  euri* 


sl-drfa  Tt^nlfi'io   eu& 


sldeiiasb  nsJlo   al  II      .6110013 
lo   nno'i   omoa   ^d  aid* 


1  3V  oo    3   as 

oio 


lo  rfo-j.,      -1B3-   a:*   lc   a^nom 

Ilulliiie    ail*  no   Ju,.baaqsb    al   boifjsn  alii"   la  aasoowa 


<i9vco   sd     a;-ncr.i 

r;   oto  Us   avlsoe'i   Ulw  qoio 


3iI     i 

l-^o  &9aloi3xs   sti  ^^r::    9i*?o   *fl9'£3  ; 


arnca  nl      .*3<ill  3d*  lo   *ns;nl-i*3D  sri*  o*  qo'io  ad* 

*«q  al  ia*svs   lo   jiUJOfftB  Bijxo   nxj   801*11*0 
ao.lTlfc&c  nl  3filsd--tqoio  .levco   ad*  'icl 

rn  3d*    io 


c* 


98 


only  by  experience  that  one  can  obtain  the  best  practice 
--each  district  having  its  own  individual  merits. 

The  amount  of  organic  matter  can  be  greatly  in- 
creased by  always  ploughing  in  the  stubble  of  the  previous 
crop.   On  no  account  should  it  be  burnt.   By  burning  all 
the  nitrogen  is  taken  away  by  oxidation  and  only  ash  left. 

A  thorough  rotation  of  crops  also  greatly  helps 
in  retaining  the  amount  of  organic  matter.   Experimenting 
in  Oregon  Professor  W.  L.  Powers  states  that  "It  is  probable 
that  the  water  requirement  may  be  decreased  one- third  where 
a  good  crop  rotation  is  practiced. " 


ic.  cJasd  ari*  n.U;tcfo  oao   enc   tad*  sousl'isqxs  -fcf 
.astern  Xejj&iviinJt  nfo  .eJJt  3aiv.ail  cfolidsik  ,1 
-ai  Tgld-fiS'-is   9cJ  HBO  isJctani  olaag'io   lo 
Jjo±y«q  sd^  lo   slo'cfucts  9ilc;-  nJt  s 

Ha  gaimwd  ^Q      .dT^;d  3d  ii   blworia   Jnyooo.s   on  nG      .c 
.dial  XI'BJS  ^Ino  6'rua  noJWsbixo  vd  ^ws  no2,8*   ai  ns 
aq.Csii  -;Id-J3ei5   oel.'s   aqoia.  lo  noWjMtorc  ifeuoio:-1-'. 


o   Ic  *nuoi-.w    sxi^    sninlcdsi  nl 

si  il"   *a*^   asJ.srJs   a^s^o-l    .1    .«  ictiesloTi  nogs-iO  nl 

ni  ctnaffioiii/pai  i9*BW   sri;   cfaiid 
ca^q   al   nol^scfcg:  qcio  60.  ps  « 


99 


CHAPTER  VIII 
THE   CROP 

In  one  of  the  previous  chapters  it  was  stated 
that  under  ideal  conditions,  irrigation  should  take  place 
when  the  soil  moisture  has  reached  a  point  somewhat  above 
the  wilting-  coefficient,  and  that  the  frequency  of  appli- 
cation would  be  dependent  on  the  time  taken  by  the  soil  to 
"dry  up"  after  the  application  of  water  to  the  next  stage 
just  above  the  wilting  point.   This  applies,  of  course,  on- 
ly theoretically.   In  practice  it  is  necessary  to  take  into 
consideration,  in  addition  to  the  above,  the  effect  of  such 
waterings  on  the  crop  itself,  at  the  particular  period  at 
which  the  water  is  applied.   It  is  not  so  much  the  case  of 
obtaining,  by  irrigation,  a  maximum  sjnount  of  dry  matter  per 
cusec  of  water  applied,  but  rather  a  maximum  yield  of  the 
useful  part  of  the  crop.   It  is  hence  of  importance  to  know 
in  what  way  the  general  growth  of  the  plant  is  affected  by 
a  variable  application  of  v/ater. 

Assimilation  and  other  processes  favouring  plant 
growth  are  especially  rapid  after  an  irrigation,  gradually 
diminishing  in  intensity  and  almost  ceasing  before  the  next 
irrigation. 

In  the  Utah  experiments  it  was  found  that  during 


n:  .  --J-0 

10HO     3HT 
BJBW  tfl  Bietfqsiio  ai/olvsiq  sild-   lo   scto  rtl 


lo   'iOflbtfpsi^  9ild-.*ai«  D       . 

ao 

S^Y;  'lo 


:LBd   e.;txl,sr;>          cfnsbnsqsft   sc!   fjlwcir  noicfso 


w-woo   lo    t3 

*  ." 

odnl.  SJiarf    cd-    ^3aa&03n  al   dU   solJo^q  nl'     .^IIsoWs^ 
rioua'io  »oell»  ari.    -svods   ad.t  '  od  npJtdloDa  nl 

'  '  "  no 


lo   38-GO    siid-  dowci  oa   c^n 
•laJda.-n  '^b   10  Jnwont: 

arlcr  Ic   M&l-j  i^'lx^i  B  i9f»si  ducf"  Vbsllqqe   I^^BW'  lo   oeawo 
won:!  ^   9ori*ioqn.I  lo   sousii  si   cfl      .qo^o   siW     lo 


al  dnclq   9i-J.   lo  ^v;q«i3     B9j»a  Uw  nl 

.i^w  lo  noi?J3olIqqB   slcfaiiav  s 

i3ild:c 


p.  »._  a  f*»« 

JIG  •- 


100 


the  first  week  after  the  irrigation  of  peas,  more  than 
five  hundred  pounds  of  dry  matter  were  added  to  the  weight, 
and  of  oats,  more  than  seven  hundred  pounds  of  dry  matter 
were  added  to  the  acre. 

The  vigour  and  general  condition  of  the  plant  de- 
pends largely  upon  the  development  of  a  good,  deep  root 
system.   In  the  early  stages  of  growth,  the  plant  uses  most 
of  the  materials  gathered  from  the  air  and  soil  for  the  de- 
velopment of  its  root  system.   When  these  are  well  develop- 
ed, carbon  assimilation  by  the  leaves  is  hastened  and  the 
growth  is  increased  rapidly.   Later  in  the  life  of  the 
plant,  the  root  growth  becomes  less,  and  the  energies  of  the 
plant  are  more  largely  directed  to  the  development  of  the 
parts  above  ground.   When  at  last  the  sterns  are  well  develop- 
ed and  a  sufficient  quantity  of  material  has  been  .stored  in 
the  various  plant  organs  the  growth  diminishes,  first  flowers 
and  then  seeds  being  developed.   It  is  important,  therefore, 
that  as  early  as  possible  the  root  system  be  made  large  and 
well  developed.   To  obtain  this  condition  it  is  essential  to 

keep  the  soil  moderately  wet  in  early  spring.   In  districts 

retentive 
where  the  winter  rainfall  is  large,  deep/soils  will  usually 

have  sufficient  water  for  the  initial  root  development  and 
no  irrigation  need  be  applied.   If  however  the  climate  con- 
ditions are  such  that  at  seeding  time  the  soil  is  not  well 


tf   eiora   ,aseq  lo 
slid1  o*  bsbbe 
-if)   Ib   afomroq 


ini   9£tt   idd-ls  aioaw  d-aill   grid- 
m  ^if>  10   aoruroq  bsibn^ii 
itevga  rtaifd-   s-iom   tcd-so  lo 

.9102     Sn':" 

lo  noWJtLnoo 
cssb    ,Loo?,   fi   lo 
aa^0  d-fljaXq  9£l*    »i»«rcis  l 
sricf  lo'i  Hod  i)hfl  IXB  9.ad-  uio'il  bensxafls  alBl«i9*Bm  arid-  lo 
tsw  sic   939:.*  -ns^W      .rn9d-a^3   Jobi   3*1    lo   d-nsmqolsv 


dd-  ncq.u 


fil  abnsq 


ai 


grid-  lc   sill   arid-  r:J    I?*- 
lc   s&ls'iang   etl*  Sn  •    ,  .aaeJ    aaaocscf 
sitf  lo   d-nomqol9vsb   9ild-  od-  osd-oe-rlfi 

.  i 

cclovsfc   II  9w  91  B   sms-j-a   eild1   d-asl   *£  ns    , 


d-uoi  siid-  ,*nslq 
sic;::  sir.  d"nelq 
-I  3.,oda 


»'i    ts.3ritiJ:nlmx.o  rid-woin   sxj      armgio   driBlq   a:/clii:v  arid- 
.d-nj3d"ic;k.-.i   ai  JI      .isqoisvai;  snlsd   a.Bssa  nerld-  bns 
«*rf  ~,i=d-?vs  jcoi   sxi*    aldlaaoq   aa  vll*®   2^   --^d- 

ill^  Jeje.'    -'      -          »" 


.in9.ias    ai  *1  nold-lbnod  Blffd-  nlad-dc  cT      .Beqolovsf)  Ilavr 

I 

d-aib  al    '  .^niiqa  \Iiae  nl  d-'sw  ^I«d-«i9bom  iioa   srld-  q 
'-f   r  r  fW  €  aansl   a^   II»'lnls-r   iOvi.;.cv.'   51^    9i9-rlw 


OJtt 


^'a    sis 


101 


is  not  well  filled  with  water,  thorough  irrigation  immedi- 
ately before  or  after  planting  is  essential  to  a  proper 
root  development.   The  part  of  the  plant  above  ground  is  al- 
so definitely  affected  by  the  quantity  of  water  applied. 
As  the  water  applied  to  the  soil  increases,  the  plant  be- 
comes longer.   With  a  lack  of  water  the  plant  remains  short. 
Not  only  the  stalks  but  also  the  proportion  of  leaves  is 
distinctly  affected  by  the  amount  of  irrigation  water  applied. 

In  a  grain  crop  the  value  of  the  straw  is  small  in 
comparison  with  that  of  the  seed.   Hence  as  much  of  the  plant 
as  possible  should  be  converted  at  harvest  time  into  seed. 
On  the  other  hand  when  a  crop  is  grown  for  forage  it  is  de- 
sirable to  secure  the  largest  proportions  of  leaves.   The 
following  extracts  from  various  reports  and  papers  fairly  es- 
tablishes the  practices  governing  these  basic  principles  of 
plant  growth. 

Alfalfa.   "Where  the  winter  and  spring  pre- 
cipitation is  sufficient,  or  where  winter 
irrigation  has  been  practiced, soils  which 
have  good  soil  moisture  retentive  power  need 
no  irrigation  before  seeding  the  first  crop, 
which  in  most  localities  generally  occurs  in 
the  spring  months  after  the  d&nger  of  kill- 
ing frosts  is  passed.   Porous  soils  which 
have  little  retentive  power  for  soil  moisture 
usually  require  irrigation  before  seeding. 
After  seeding  the  young  alfalfa  plants  should 
receive  no  further  irrigation  until  the  plants 
show  the  need  for  water  or  even  not  until  they 
show  signs  of  suffering  for  lack  of  moisture;  • 
this  is  desirable  to  develop  the  root  system 


ilcflw  bellil  Haw  don  si 

isqoiq   s  od-  JJal^nSiUS   al  ?;ni^n'slq  iscM:?   -10   s^cclaci  - 
-is   ai  bflJUOT-p,   avodB  dri-ilq  oJd1  'lo  d^i^q   sifj?      ,rfr:e;,tqoi9V9f) 

.ballqqa  iscfsw  lo  tt'ltxaup  srW  ^d  L'sJoaTia  ^lacMnllsb  oe 
-scf  cfnalq  oild-    (S^aBs-ionl   lioa  .  erW  c-i   bsilqqs   lactsw  snct   aA 
druaiq  ed^  risc}-BW  lo  ;-lO3l  2  if.j-iW  •  .lesnol   aantoo 

IJ»S^« 

i  'lo   Jrtuoms   3iJ   -jc!  b9cios'iri.j3  ^I 


ai  wa'icfa   srl*  lo    9.c/I?.v   arid"   qo-io  niai^   &  nl 


nc 

fiBlq   9£fj  "io  ilojjn:  aa  eonoH      .bssa   srlct  lo 

.59.33   oo'ni   sfi-l-d-   uasv:1:      d..j      siisvneo   .scf  Blwoila   siu'laacq  as 
-si)   ai  it  3g*»iol  'io'i  nv/oi3  al  qo'.ro   a  nsrfv; 
adT      .  ssvn^I  lo   3ncJ:Trioqor;q  J-s^gisI    3uj 
as   -;ir:i.3l   a-£';?qsq  Lrca   c,  Jioca-i   ajjciri^v  nto  .'1   aJ- 
lo   aslc  Ior.ifiq   oxasc.'  oaeiid   gnin'iovoa  aeoiaO-Jiq 


•:-.  ,.aiw  exit    pnorii"       . 


913-  .'.v  -iv.    .di-sioiilwa   ai  nol-isjiqio 


fcisan  'lowoq  gsviin^is'i   eij^aloct  iioa  .1x^05  evsii 
»ocrio   d-erril    o/ii   sai^Dss   d-iclscf  asid.c3iiii   on 


T1        r^\      r*      v*r-  e*r~r      «v  r>  -         'i       of    -    r*/-  «•*      1-1  -•  "  " 

liolrlw  alioa   «sjuoio*i      .baaaaq   si  1   ;inl 

91  llO3    'lol    T9WOq    ?V  '  "j  11    SV6.CI 


32   -.sd-'iA 
:.n  t->v 
;n  srlj 
2  .artgia 


102 


downward  instead  of  confining  it  to  the 
surface, as  may  occur  with  too  early  ir- 
rigation.  The  root  system  can  be  fur- 
ther strengthened  by  cutting  the  young 
alfalfa  when  eight  inches  high.  When  the 
alfalfa  has  established  a  well  -developed 
root  system  thecommon  practice  on  reten- 
tive soil  is  to  ap  ply  one  irrigation  be- 
fore or  after  cutting.   On  gravelly  por- 
ous soils  and  on  shallow  soils,  two  or 
even  tiiree  irrigations  for  each  cutting 
may  be  necessary.^/ 

Cereals.   "The  soil  should  contain  suf- 
ficient moisture  at  the  time  of  seeding 
to  germinate  the  seed  and  to  start  the 
plants  growing.   No  irrigation  before 
seeding  is  required  for  a  retentive  soil 
when  winter  precipitation  is  not  too 
small,  or  when  the  soil  moisture  has  been 
supplied  by  winter  irrigation.   Irriga- 
tion before  seeding  is  necessary  for  a 
soil  which  is  too  dry  because  of  defici- 
ent winter  precipitation  or  irrigation. 
Where  irrigation  before  seeding  will  keep 
the  ground  wet  too  long  and  delay  the 
seeding,  it  may  be  necessary  to  irrigate 
immediately  after  planting.   This  prac- 
tice is  objectionable  for  soils  that  have 
a  tendency  to  bake;  it  increases  the  evapo- 
ration loss  and  requires  an  earlier  second 
irrigation. 

After  the  plants  have  germinated,  the  first 
irrigation  should  not  be  applied  until  the 
plants  require  it,  but  before  the  plants  be- 
gin to  suffer  for  moisture,  which  for  a 
moderately  retentive  soil  will  be  tv/o  or 
three  months  after  seeding  when  the  plants 
shade  the  ground  and  have  grown  to  a  height 
of  six  to  nine  inches.   A  second  irrigation 
is  usually  necessary  when  the  heads  just 
begin  to  form,  and  a  third  irrigation  is 
often  desirable  when  the  heads  are  filling 
out.   The  practice  will  vary  especially 
with  the  character  of  the  soil  and  the  time 
and  extent  of  precipitation;  a  good  reten- 


ei:d-  o*  J-l  gnlnllnoo  lc  bsetfanx  crr; 
-itft   sd'nso'niad-aie   *oorc   9rTi;      •       '.J :••••*'& 


iisil»<      . riT  ill  B9rlonx  Jil§i9  r; 
bsqoi'9V»b- 1I9-.7  s  6«£l3iXda*88-  aaii 
nc   soid-os-iq  noffimoogiid 

-9d''hc.iJ-*5"".  illi    WIQ    Tu-tq  OJ5    °*    si    i-ica    sv 

-r--oc     llav/i^'    n'C      .^rijocf.uo  ri3d"i.e  rio 
:-    ,  aiioa   v/cll 
o   ifoBS   "rol   anc 


-Iwa  ni^^rtvO   biwoJifi   Ilos   0-1T 


Ic   srf.icJ   9il---    *.s    3i^sior. 

a   oct  bna  bssa   adi'^i         .:ri3S  o* 
Biolsd  aclJB3±.Txi  o'/i     .gniwcia  al 

lioe    5V.tci-ne75ri     :  rid  Lj-iJr^pai   tl 

oo*   tfcn  3i  nololB"lqlo9'iq  lo^ni  ?  nsaw 
aari  s'irJaio::i  Hoi   srl*  n«n'vr  ^c    ,1.1 

iflsimi  ri^ 

' 


lo    9s,u.3osd  V-t^  oo:J   a*  iloMw  lioa 
Jtiii  'io  rtcii      Iqioaiq 
Ill«r  ^nibe-32  9*1  clod  noliflgx-rrl   9'i9--',V 
-flleb  I>ac  aaol   oo*  Jgw  broraig  sii* 

o+    ^-laassosn.  9(5  ^an  cfl 
iiT    J.'snIdTi--.iq  10*!^  ^leJslbanmti 
aiioa   riol  slcf^ncid-oe'Qo'.o  si  90! 
s's  3nl  *1    {  93ffld  ocf    ^onsbnsd 
ru   2?tiJJp3-i   bar    sad  nci'i 


-sd  aixiBlq  srLi   sclscf  *urf  •».*!  eii 

a  ic!  ifoirlw   t9i«*axom  tol  is!'.. 


a^rcla  slid"  nsd'.?  ?vxi&99<3  13^13  a.linofti 

B^'od- 

•     •  'ivtl  fcno39a  A      .as^oci  r   xia  lo 

*.„                            3ild    «9ii.?     ;       -  TjII^WSiJ    31 

•         •                       •  i  OT 

««--r  '  --:- 


103 


tive  deep  soil  with  a  moderate  winter 
and  spring  precipitation  may  require 
only  one  late  irrigation  when  the  heads 
just  begin  to  form;  a  porous  soil  may 
require  four  light  irrigations."/^ 

"In  a  number  of  irrigation  experiments 
with  grain  the  best  results  were  obtain- 
ed both  in  quantity  and  quality  of  yield 
with  three  irrigations  at  the  jointing, 
booting  and  soft  dough  periods.   At  the 
jointing  the  embryo  head  is  forming,  at 
the  booting  it  is  about  to  emerge  and  at 
the  soft  dough  the  kernel  is  f  illing. 


"At  the  Utah  Station  the  growth  of  wheat 
was  divided  into  four  stages  (1)   when 
five  leaves  had  developed  and  the  plants 
were  6"  —  8"  high  (2)  the  early  boot 
stages  when  the  plants  were  just  swelling 
preparatory  to  heading  (3)  the  bloom 
stage,  when  most  of  the  plants  v/ere  in 
bloom  and  (4)  when  the  plants  were  in  the 
dough  stage.   The  experiments  were  con- 
ducted on  a  loam  soil.   The  experiments 
were  conducted  on  a  loam  soil.   The  pre- 
cipitation averaged  17.8  inches  and  37.3 
bushels  per  acre  wer-e  raised  without  ir- 
rigation.  The  highest  yield  of  wheat  was 
produced  with  three  irrigations  of  five 
inches  each  applied  at  the  five  leaf,  the 
early  boot  and  the  bloom  stages.   Irriga- 
tion applied  after  seeding  before  the 
grain  was  up  and  that  applied  after  the 
dough  stage,  decreased  the  yield.  Where 
only  one  irrigation  was  given  the  best 
time  to  give  it  was  at  the  five  leaf 
stage;  where  two  irrigations  were  used 
the  five  leaf  stage  and  boot  stage  were 
best;  where  three  irrigations,  the  five 

leaf,  boot  and  bloom  stages  were  best." 

' 


Potatoes.   "Retentive  soil  except  for 
late  planting  is  usually  sufficiently 
moist  from  the  winter  and  spring  precipi- 
tation to  require  no  irrigation  before 


- 


.  ,artWrtlot    9^*   *a   anolcfr  a^Tii      aid*  a 

d-A      .a&ol'ie-  dw 

'*s    ,snl.7.icl   a  I   ossrl  o^tftro   sd  '   3/1  j 
d-s  bna  9^1  sine  od"  ctrods  2!  *i  snl^oocf 
al   isnioii  srict   rfai/ob 


ilw  lo  rfctwoi*  erW  nol^s^a  rte^U  sri* 
rtsriw      U)    W>i   -wol  oinl  bsbivlfc.  saw 

q  artt  bn  •  b?co.^vei   ! 

Soocf  ^lijao   srfo    IS)   ^S-^i     3-- 

lairt   9^3";  aJnslfl  ad; 
nicolcr   srij-    (S)    gt  iiasi-'O.*  i^o/a'ia 
nx  d-iaw  a-^nslq  sri*   lo  taotn  neaw   ,s^e^a 
at  *^w.e*n*Jq    )*»  n«ffW{-*)   ftoa  nwold 


Rtt^E^ft>^    ^^      '.IlOB  '  SIBOl    B    HO 

-o-ic  "adr"    ..Iloa   m&ol   B   no  £9^cw& 
6.t*5*f>ni   asrlDnJt-.-  8.  VI  be^isv^  noilBd 

lit   *trorf^Jtw  beBijri  9--ewWss  i-3q  al 
aaif  tfaariv?  lo  blsl^  Iso^lrJ  sriT      .noj 

evil  Ic    anblt?giiil   sarfiid'  rldiw  b«owbciq 
arlj    ,lsei    wrll  ^1  ^«   b^ilqqs  if»fl9   8?no«i 

-aglTil      .333^3  -••^1  t?°      "      4 

siict    en^ls'J  -^JLoaa  i9*la  b&iiqq*  1 

lad-la  beiiqqa  iartt  bno  qi;  a»» 

lalv  ' 

o.r-  jaw  nclj;'3i': 

6V  f'l    9:13     is     33W    itl     C  ';^^ 

~ 


J    ,lJ39£ 

.  2_ 

js  ' 


104 


seeding.   Dry  soil  must  be  irrigated  be- 
fore planting.   Planting  in  dry  hot  soil, 
followed  immediately  by  irrigation  is  not 
desirable.   Daring  the  first  stages  of 
growth  throughout  cultivation  is  more  im- 
portant than  irrigation,  and  no  irrigation 
may  be  necessary  until  July.   Too  early  ir- 
rigation after  planting  may  compact  and 
bake  the  soil  around  the  roots.   Potato 
vines  are  shallow  rooted  and  frequent  irri- 
gations, especially  early  in  the  season 
when  the  water  is  cold,  will  retard  the 
growth;  for  this  reason  some  irrigators 
prefer  to  apply  the  water  at  night,  when 
the  soil  and  water  have  had  all  day  to  warm 
up  in  the  sun.   The  moisture  in  the  soil 
should  be  kept  fairly  uniform  until  the  tu- 
bers begin  to  form,  when  a  heavier  irriga- 
tion is  generally  required.   The  soil  should 
not  be  allowed  to  harden  around  the  roots. 
The  last  irrigation  should  be  applied  before 
the  growth  of  the  tuber  ceases,  in  order  to 
give  about  1&--2  months  for  ripening  in  dry 
earth.   The  number  of  irrigations  will  vary 
from  two  to  four  for  sandy  loam  and  from 
four  to  six  light  irrigations  for  a  porous 
sandy  soil  or  a  shallow  soil.   The  need  of 
irrigation  may  be  indicated  by  the  appear- 
ance of  the  plants;  dark  leaves  indicate  a 
lack  of  moisture,  light  yellowish  green 
leaves  indicate  an  excess.   An  examination 
of  the  soil  where  the  tubers  form  is  an- 
other good  indication.   A  sandy  soil  is  in 
good  condition  when  a  ball  of  earth  squeezed 
in  the  hand  will  retain  its  shape. 


Cotton.   "Soils  for  cotton  should  be  given 
sufficient  moisture  for  germination  before 
planting.   With  cultivation  no  further  ir- 
rigation should  be  required  for  six  weeks 
to  two  months.   From  two  to  four  light  irri- 
gations are  given  during  the  period  of  plant 
growth.   Too  heavy  irrigations  at  this  time 
results  in  excessive  vegetative  growth  at 
the  expense  of  crop  production.   After  about 
July  1st,  the  crop  on  most  soils  will  re- 


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quire  irrigations  at  ten  to  fifteen  days 
intervals.   While  some  wilting  in  the 
early  season  may  not  be  harmful,  at  the 
flowering  period  moisture  should  be 
maintained  so  that  no  wilting  will  occur. 
One  or  two  irrigations  after  the  first 
picking  are  usual  .  n 


Orchards.   Deciduous  trees  are  deep  rooted  when 
the  soil  conditions  are  favourable;  they  require  less  water 
than  other  irrigated  crops  and  for  that  reason  the  need  for 
irrigation  is  not  so  apparent.   Citrus  trees  are  not  as  deep 
rooted  as  deciduous  trees;  they  are  evergreen  and  therefore 
the  evaporation  from  their  leaves  is  continuous  and  the  max- 
imum moisture  need  for  fruit  growth  is  in  the  fall;  for  these 
reasons  citrus  trees  require  more  irrigation  than  deciduous 
trees. 

Pall  and  winter  irrigation  is  very  advantageous 
in  the  maintenance  of  orchards,  where  the  greater  part  of 
the  rainfall  does  not  occur  in  these  periods.   As  a  general 
rule  trees  must  not  be  irrigated,  or  very  cautiously,  when 
they  are  in  bloom,  for  such  early  irrigation  is  said  to  in- 
terfere with  the  setting  of  the  fruit. 

"Orchard  soils  should  not  be  allowed  to 
dry  out  too  much  for  an  excessive  dry- 
ness  in  early  or  middle  summer  will  in- 
jure the  tree  for  the  whole  season.   On 
the  other  hand,  over-  irrigation  tends  to 
decrease  fruit  production  and  delay  the 
ripening  .  Y& 


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106 


The  last  irrigation  is  given  in  the  first  week  of  September, 
so  that  the  new  wood  may  have  a  chance  to  mature  before  any 
freezing  occurs.   This  late  irrigation  also  has  the  advan- 
tage of  keeping  the  leaves  somewhat  longer  on  the  trees, 
aiding  thereby  the  formation  of  the  new  wood. 

Young  trees  should  not  be  irrigated  .more  than 
once  or  twice  a  season.   This  is  essential  to  the  formation 
of  a  deep  drought  resisting  root  system.   Professor  Wickson 
draws  the  following  conclusions: 

"For  deciduous  fruit  trees  on  deep  soils, 
fairly  retentive,  ten  inches  of  irrigation 
water,  applied  at  the  proper  time,  during 
five  months  of  growth  and  fruiting,  accom- 
panied by  good  cultivation,  is  sufficient, 
even  when  the  rainfall  is  only  about 
enough  to  prevent  drying  out  during  the 
winter. 

For  citrus  trees  twenty  inches  of  irriga- 
tion water  is  usually  sufficient  where  the 
rainfall  is  considerable  and  for  the  more 
retentive  soils,  ten  inches  applied  at  the 
right  time  may  be  adequate." 

A  diversification  of  the  irrigated  crops  will  usu- 
ally result  in  an  increased  duty.   The  reasonable  water  re- 
quirement should  not  be  based  on  the  needs  of  the  crop  of 
maximum  water  requirement  but  rather  on  the  average  water  re- 
quirement for  the  entire  ares, --the  average  being  of  course 
proportional  to  the  areas  which  each  type  of  crop  occupies. 
By  diversifying  his. crops  the  farmer's  need  for  water  will  be 


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107 


more  uniform  and  constant,  instead  of  the  greatest  need 
for  water  falling  within  a  comparatively  short  period. 
The  same  applies  to  an  entire  irrigation  project,  helping 
materially  in  the  proper  distribution  of  water  by  rotation. 
The  greater  the  diversification  of  the  crop  the  more  uni- 
form will  be  the  required  capacity  of  the  main  canal. 

i.  x   :--T™,'  if  k->tc*-tl-<U 

If  a  majority  of  the  acreage  of  any  project  is 
planted  to  one  particular  crop,  say  alfalfa,  it  is  impos- 
sible to  serve  adequately  all  of  the  land  in  that  crop  at 
the  time  of  greatest  demand,  unless  the  canal  has  been  de- 
signed with  a  large  excess  capacity  for  that  particular  pur- 
pose.  Most  of  the  other  crops  such  as  grains,  potatoes, 
corn,  beans,  cotton,  etc.,  have  a  lower  water  requirement 
and  their  maximum  demands  do  not  extend  over  as  long  an  in- 
terval of  time  as  that  of  alfalfa  or  are  not  of  the  same 
magnitude.   The  results  from  the  Cache  Valley  experiments 
illustrate  this  very  clearly.  (See  Figure)   In  fact  some  of 
the  crops  of  low  water  requirement  such  as  fall  planted 
grains,  early  potatoes,  strawberries,  etc.,  may  be  cared  for 
entirely  before  the  time  of  peak  load.   Other  crops  of  low 
total  water  requirement,  but  which  may  require  water  during 
the  peak  of  the  season,  are  corn, beans,  sorghums,  etc.   Po- 
tatoes and  sugar  beets  may  require  as  much  water  as  alfalfa 


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s. 


108 


during  the  two  months  of  the  peak  loads,  but  on  a  given 
farm  are  not  likely  to  require  service  at  the  same  time. 

In  crop  selection  and  carefully  planned  crop  ro- 
tation may  be  found  one  of  the  most  practical  means  of  re- 
ducing the  peak  load  of  an  irrigation  system  and  maintaining 
a  generally  high  water  duty.   If  this  peak  can  be  distributed 
through  the  season,  it  will  result  in  a  lower  construction 
cost,  and  in  many  economies  in  operation  and  maintenance. 


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m  nl  bru 


109 


CHAPTER  IX 

YIELD  OP  VARIOUS  CROPS  UNDER  VARYING 
AMOUNTS  OF  IRRIGATION  APPLICATIONS 

Under  the  direction  of  Dr.  Harris  of  Utah  a  very 
complete  set  of  experiments  has  been  conducted  to  determine 
the  effect  of  varying  quantities  of  water  on  the  crop  yield. 
The  experiments  were  conducted  in  Cache  Valley,  Utah,  and 
extend  over  a  period  of  some  fourteen  to  seventeen  years, 
•hilst  of  course  these  results  are  ^strictly  only  of  practic- 
al benefit  to  the  area  concerned,  it  nevertheless  gives  an 
accurate  reflection  of  conditions  under  which  a  maximum  of 
various  crops  may  be  obtained.   The  results  obtained  are  re- 
produced below,  together  with  results  obtained  from  various 
other  sources. 

Irregularities  in  yield  are  often  traceable  to 
the  fact  that  the  complete  series  were  not  run  through  all 
the  years.   It  must,  therefore,  be  kept  in  mind  that  exact 
yields  cannot  be  given  too  much  weight.   It  will  be  much  sa- 
fer to  take  the  results  as  a  whole  rather  than  any  one  fig- 
ure or  point  on  the  curves.   In  the  case  of  the  Utah  curves 
the  actual  average  yield  for  the  different  irrigations  are 
shown  by  the  dotted  lines,  while  the  heavy  line  represents  a 
medium  yield  obtained  by  considering  the  average  of  the  great- 


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110 


er  number  of  tests  to  be  nearer  to  the  true  average  than  the 
average  of  a  fewer  number  and  weighing  accordingly.   A  one 
year  test  is  not  given  the  same  weight  in  arriving  at  a 
point  for  the  heavy  curve  to  pass  through  as  a  test  covering 
several  years. 

The  following  table  shows  the  average  of  a  total 
of  one  hundred  seventy-six  trials  extending  through  fourteen 
years. 


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The  Utah  results  are  tabulated  in  Table  XXX 
and  illustrated  in  Figure  XVII. 

Alfalfa   (Lucerne J 


Acre  inches 
water 

Number  of 
trials 

Number  of 
years 

Yield  in  tons 
per  acre 

,.„ 
0 

14 

r 

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11 

2,655 

5 

36 

7 
i 

3,233 

10 

28 

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11 

3.923 

12.5 

3 

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3,783 

15 

30 

14 

4,294 

20     5 

12 

-. 

12 

4.165 

22.5 

1 

1 

4.090 

25 

14 

12 

, 

4.544 

30 

10 

- 

10 

4.515 

32.5 

2 

0 

4.841 

35 

3 

3 

: 

4.198 

37.5 

1 

1 

4.400 

40 

4 

4 

3.740 

45 

2 

2 

4.613 

50 

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8 

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8 

5.355 

52.5 

2 

2 

3.718 

60 

1 

1 

4.691 

65 

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1 

3.399 

67.5 

1 

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75 

1 

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113 


In  the  Modesto  Turlock  district  investigations 
were  conducted  during  the  years  1916,  1917  and  1918.   The 
results  are  shown  in  the  following  Table. 

TABLE  XXXII/?3,/ 


Check  No. 

1916 

1917 

1918 

Amount 

Total 

'Amount 

Total 

Amount  'Total 

of  water 
applied 
inches 

yield 
tons  per 
acre 

of  water 
applied 
inches 

yield 
tons  per 

acre 
• 

of  wa- 
ter ap- 
plied 
inches 

yield 
tons 
per 
acre 

1 

50.04 

7.68 

-- 

- 

41.86 

6.64 

2 

56.05 

8.74 

68.44 

6.75 

55.01 

5.06 

5 

22.06 

8.01 

29.42 

6.92 

45.44 

6.17 

4 

17.21 

7.91 

•* 

21.59 

6.94 

18.45 

6.41 

5 

25.25 

8.91 

29.75 

6.96 

58.71 

6.58 

/•» 

22.59 

8.75 

55.12 

7.09 

28.11 

6.75 

7 

29.41 

9.52 

44.42 

7.00 

47.75 

6.45 

8 

28.95 

9.56 

45.64 

7.64 

56.99 

6.65 

9 

26.72 

8.9 

47.77 

4.25 

.  . 

41.95 

5.71 

In  Oregon--at  Corvallis — similar  experiments  were 
conducted  for  the  purpose  "of  determining  the  value  of  irri- 
gation for  increasing  and  insuring  productiveness  of  the 
agricultural  lands  in  the  semi-humid  Willamette  Valley." 


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114 


The  following  Table  shows  the  results  on  Alfalfa 


TABLE  XXXIII //// 


Year  and  Treatment 

Total 
yield 
in  tons 
per 
acre 

A. 

Value  of  harrowing  and  irrigating  for 

B. 

new  seeding 
1911  (seeded  1909  without  irrigation) 
1911  (seeded  1909  with  irrigation  harrowed) 
1911  (seeded  1909  with  irrigation  unharrowed) 
1912  (seeded  1909  without  irrigation) 
1912  (seeded  1909  with  irrigation  harrowed) 
1912  (seeded  1909  with  irrigation  unharrowed) 

Irrigation  before  and  after  cutting 

2.17 
4.16 
4.08 
4.00 
5.42 
4.10 

G. 

1911  6"  before  cutting 
1911  6"  after  cutting 
1912  2  irrigations  of  5"  before  cutting 
1912  2  irrigations  of  5"  after  cutting 

Furrows  versus  flooding 

4.41 
4.59 
10.37 
10.30 

D. 

1912  one  5"  irrigation  with  furrows 
1912  one  5"  irrigation  with  furrows 

Amount  of  irrigation 

6.37 
5.17 

1911  2  irrigations  of  4",  total  8" 
1911  3  irrigations  of  4",  total  12" 
1912  2  irrigations  of  4",  total  8" 
1912  2  irrigations  of  6",  total  12" 

1915  (seeded  1909  without  irrigation) 
1913  1  irrigation  of  4",  total  4" 
1913  1  irrigation  of  6",  total  6" 
1913  2  irrigations  of  4",  total  8" 

4.51 
5.22 
6.70 
7.75 

2.15 
3.80 
4.22 
4.22 

Alfalfa  was  weighed  as  green  feed  in  1912  and  as  cured  hay 
in  1911  and  1913. 


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115 


The  experiments  conducted  at  Idaho  during  1910 
•1914  give  the  following  summarized  results. 

TABLE 


'Class  of 

'soil 
i            i 

Average  depth 
of  water  ap- 
plied in  feet 

Average  yield 
in  tons  per 
acre 

i 

'Clay  loam 

'areas 

i 

'Areas  making 
'maximum 
'yield  in  eact 
'experiment 

I 
2  .  40 

• 

." 

2.73 
i 

4.91 
5.47 

An  examination  of  the  results  for  alfalfa  shows 
that  this  crop  can  profitably  use  much  larger  quantities  of 
water  than  most  other  crops  grown  under  irrigation.   There 
is  a  decline  in  yield  after  a  certain  maximum  amount  of  wa- 
ter is  applied,  but  the  decline  is  slow.   Alfalfa  is  seen  to 

i- 

be  much  less  sensitive  to  over  irrigation  than  potatoes  and 
cereals.   The  Utah  results  show  a  maximum  yield  with  fifty 
acre  inches,  although  twenty- five  inches  gave  very  nearly 
the  same  amount  i.  e.  a  saving  of  fifty  percent  of  water 
gave  only  a  15.2  percent  decrease  in  crop  yield. 

In  the  case  of  the  Davis  experiments  at  the  end  of 
the  six  year  experimental  period,  the  stand  on  the  areas 
given  the  heaviest  irrigations  was  only  27  percent  of  the 
original  stand,  the  excess  use  having  enabled  grass  to  come 


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116 


into  the  alfalfa.   The  best  stands  at  the  end  v/ere  areas 
given  thirty  to  thirty- six  inches  of  water, --which  is  un- 
doubtedly the  most  desirable  quantity  for  the  irrigation 
of  alfalfa  under  general  Sacramento  Valley  and  San  Joaquin 
Valley  conditions. 

In  1918  the  best  yield  at  Modesto  was  with  a  to- 
tal depth  of  28.11  inches. 

In  Oregon  Professor  Powers  conies  to  the  follow- 
ing conclusion,  "The  maximum  yield  of  alfalfa  in  all  trials 
has  been  secured  in  the  dry  seasons  with  ten  or  twelve  in- 
ches of  water,  but  in  wet  seasons  with  six  inches  of  water. 
The  most  economical  increase  in  yield  with  irrigation  has 
been  secured  with  four  to  six  inches  of  water." 

Potatoes.   Table  XXXV  and  Figure  XVIII  show  the 
Utah  results  for  this  crop.   Although  considerable  variation 
is  noted  in  the  trials  during  the  different  years  (the  ex- 
periments extended  through  fourteen  years  and  the  Table  shows 
the  average  of  two  hundred  sixteen  trials),  the  general  ten- 
dencies are  distinct.  The  most  favourable  amount  of  water  for 
potatoes  seems  to  be  between  thirty  and  forty  inches.   For 
applications  above  sixty  inches  the  yield  drops  very  rapidly. 
This  is  probably  due  in  part  to  the  fact  that  excessive  water 
prevents  the  tubers  from  securing  the  supply  of  air  needed 
for  optimum  growth. 


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117 


TABLE  XXXV  faj 


Acre  inches 
applied 

'No.  of 
'trials 

No.  of 
years 

'Yield  in  bushels 
per  acre 

None 

12 

12 

117.37 

2.5 

4 

4 

157.19 

5.0       --J 

.  . 

39 

14 

162.23 

7.5 

20 

9 

165.38 

10 
12.5 

39 

4 

14 

r  W               I 

4 

217.24 
284  .  87 

15 

39 

14 

228.62 

17.5 

1 

1 

1   293.75 

20 

13 

13 

266.53 

22.5 

2 

2 

2   321.18 

25 

4 

4 

204.02 

27.5 

2 

2 

345.50 

30 

7 

7 

269.92  * 

52.5 

4 

4 

377.59 

40 

- 

2 

.  2 

341.44 

45 

8 

8 

271.39 

50 

1 

1 

83.45 

55 

3 

3 

240.00 

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1 

246.00 

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1 

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1 

1 

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2 

1 

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The  Oregon  results  are  as  follows: 
TABLE  XXXVI/'// 


Year  and  Treatment 

Yield  in 
bushels 
per  acre 

1911--a 

dry  season 

Dry 

135.1 

3  irr 

igations  of 

1"  *     \ 

250.9 

1 

ii       it 

3" 

176.4 

2 

ti       ti 

2|f" 

240.7 

i 

1 

n       ii 

5" 

190.9 

5 

ti       ti 

2  " 

254.9 

2 

it       n 

3" 

258.1 

2 

»       n 

3" 

308.5 

3 

n       n 

3" 

292.5 

1913--wet  season 

Dry 

109.8 

1  Irrigation  of  2 

n 

172.2 

1 

ii      n  5 

ii 

213.3 

2 

n      n  2 

n 

145.2 

The  average  results  with  potatoes  at  Gooding, 
Idaho,  for  the  four  years,  1910--1914  are  in  Table  XXXVII 


39 


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119 


TABLE  XXXVI I  //J 


1 

No.  of  irriga- 
tions 

r 

Total  water 
applied  in 
feet 

Yield  tons 
per  acre 

2       1 

.69  - 

3.2 

4 

1.72 

6.75 

6 

2.85 

6.7 

In  Oregon  the  maximum  yield  for  the  wet  season 
was  with  three  inches  of  water,  while  in  the  dry  season  it 
was  with  six  inches  of  water.   The  most  economical  yield  of 
potatoes  obtained  in  the  course  of  the  experiments  was  se- 
cured with  the  aid  of  three  one  inch  irrigations,  applied 
ten  days  apart,  giving  a  yield  of  58.6  bushels  per  acre 
inch . 

In  Idaho,  the  conclusion  was  reached  that  it 
would  not  be  advisable  or  profitable  to  apply  more  than  two 
to  two  and  one-half  acre  feet  per  acre  on  clay  loam  soils. 

Cereals.  Experiments  at  Utah  on  corn  were  conduct- 
ed through  a  period  of  seventeen  years  with  the  following  re- 
sults, given  in  Table  XXXVIII  and  Figure  XIX. 


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120 


TABLE 


Acre 

inches 
applied 

fNo  .  of 
trials 

ft'o  .  of 
years 

'Yield  in  bu- 
shels per 
acre 

Hone 

13 

13 

57.33 

5 

13 

13 

61.39 

7.5 

8 

8 

79.14 

10 

17 

17 

77.23 

15 

8 

8 

93.93 

20 

17 

17 

81.80 

25 

8 

8 

99.16 

30 

17 

17 

81.49 

40 

,  9 

9 

65.30 

55 

8 

8 

' 

96.78 

On  the  San  Joaquin  and  King's  River  Canal  system 
the  follov/ing  results  were  obtained. 

TABLE  XXXIX 


fear 

'  Depth 
plied 

of  water  ap- 
in  feet       J 

1907 

2.13 

'1908 

1.65 

1911 

1.38 

Aver 

•age 

1.72 

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121 


The  Utah  results  on  wheat,  extending  through  a 
period  of  thirteen  years  are  given  in  Table  XL  and  Figure 
XX. 


Acre 
inches 
applied 

No.  of 
trials 

r— 

'Ho.  of 
years 

i 
Yield  per  acre 

Grain  'Straw 
bushels'  pounds 

None 

9 

9 

"i 

38.37'  3982 
i 

5 

34 

13 

38.23  '  3540 
i 

7.5 

18 

9 

41.54'  3301 
i 

10 

38 

13 

42.90'  4142 
i 

15 

34 

13 

47.10  '-4796 
i 

20 

4   -J 

-   4 

45.70  '  5940 
i 

22.5 

4 

4 

,  ', 

44.60  '  6757 
1 

25 

18 

9 

46.46  '  4311 
t       i 

35 

18 

9 

48.55'  4755 
i 

45 

4 

4 

45.80  '  6250 
i 

50 

18 

9 

49.38  '  5332 
t 

67.5 

4 

4 

43.50  '  5794 
i 

boxieq 

.XX. 


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122 


The  experiments  at  Gooding,  Idaho,  gave  the  follow- 
ing results. 

TABLE  XLI 


No.  of  ir- 
rigations 

Total  water 
absorbed  per 
acre  foot 
per  acre 

Yield  of 
grain 
bushels 
per  acre 

0 

- 

0 

13.3 

•i 

. 

.36 

23.3 

3 

.75 

28.7 

4 

1.23 

31.8 

6 

1.76 

33.1 

8 

2.27 

36.0 

9 

2.94 

27.5 
t 

Results  on  wheat  experiments  at  Davis,  California, 
during  1912-1914  gave  the  following: 


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*r.-rc  ,  alvBu  d-s  a^ne;iti'X3UX6   .issiiw  no 


123 


TABLE  XLII 


No.  of  ir- 
rigations 

Depth  ap- 
plied 

Yield  ir 
ger  a 

L  pounds 
ere 

1 

inches 

Hay 

Grain 

0 

-- 

2703 

657 

1 

6.0 
t 

4267 

1157 

2 

10.1 

• 

6100 

1529 

2 

15.5 

5050 

1029 

Typical  practice  is  represented  by  Table  XLIII 
which  shows  the  net  duty  on  grain  in  the  San  Joaquin  Valley 

TABLE  XLIII 


Year    'Depth 

applied  ft. 

i 

1907   ' 

.74 

i 

1908   ' 

.84 

i 

1911   ' 

.96 

i 

1915   ' 

1.11 

i 

Average 

.91  ft 

At  Utah,  oats  gave  the  following  results  for  a 
period  of  six  years- -Table  XLIV  and  Figure  XXI. 


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124 


TABLE 


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Acre 

No.  of 

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No.  of 

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Yield  per  acre 

inches 

trials 

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years 

applied 

' 

Grain  in 

Straw  in 

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bushels 

pounds 

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None 

6 

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6 

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6    ,. 

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15 

18 

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6 

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6 

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On  the  whole  it  will  be  seen  th-  t  the  yield  of 
cereals  is  not  nearly  so  much  affected  by  irrigation  as  is 
the  case  with  potatoes  and  alfalfa.   In  the  case  of  the 
Utah  experiments  on  wheat,  for  instance, fifteen  inches  of 
water  gave  almost  as  high  a  yield  as  any  treatment  and  yet 
the  yield  kept  up  fairly  well  with  the  very  heavy  irriga- 
tions.  It  will  be  noted  that  where  no  irrigation  water  was 
applied  the  yield  of  wheat  were  fairly  satisfactory.  There- 
fore, in  practice,  it  is  doubtful  whether  more  than  fifteen 
inches  of  water  would  pay  for  the  extra  yield  obtained. 

Oats  is  a  plant  which  is  more  sensitive  to  mois- 
ture than  wheat.   In  the  Utah  results,  there  is  a  gradual 


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125 


increase  in  the  yield  with  an  increase  in  water  up  to 
thirty  inches,  above  which  the  yield  decreases  slightly. 
The  yields  were  not  greatly  different  for  quantities  of  wa- 
ter between  fifteen  and  forty- five  acre  inches. 

The  results  on  corn  show  the  highest  yield  with 
twenty-five  inches  of  water,  although  yields  are  almost  the 
same  for  all  quantities  of  water  between  fifteen  and  thirty 
inches.  While  the  yields  were  somewhat  reduced  by  exces- 
sively large  irrigation  applications,  this  w-.s  not  nearly 
so  much  the  case  as  with  potatoes. 

Citrus  Fruits.   In  the  State  Engineers  Report 
(California)  for  1912- -1914,  the  following  data  of  the  net 
duty  on  citrus  fruits  to  Southern  California  are  given. 


'£9*sw  til   33^9'ioni  rta  ridiv;  b.,3i^   3ild~   at 


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TABLE  XLV 


126 


Location  and  Source  of  Supply 

i 

1  Year 
i        .  J 
i 

i 

Acreage 

Depth 
of  wa- 
ter 
applied 
feet 

Gage  Canal  and  Riverside 
Water  Companies 

i 
i 

'1899-1905 
i 

80,667 

2.25 

Riverside  Water  Company 

'1901-1908 
i 

9,000 

2.29 

Riverside  Water  Company 

'1912 
i 

31.5 

4.10 

Riverside  Water  Company 

'1912 
i 

19 

2.58 

Santa  Ana  Valley  Canal 

'1912 

20 

1.79 

Santa  Ana  Valley  Canal 

|1912 

18.4 

1.52 

Del  Monte  Irrigation  Company 

'1906 
i 

2,000 

.73 

Del  Monte  Irrigation  Company 

'1907     : 
i 

2,000 

1.10 

Del  Monte  Irrigation  Company 

'1908 
i 

2,000 

- 

.73 

Del  Monte  Irrigation  Company 

'1909 
i 

2,000 

;   ,.73 

Palomares  Irrigation  Company 

'1906 

i 

600 

.71 

Palomares  Irrigation  Company 

'1907 
i 

600 

.83 

Palomares  Irrigation  Company 

'1908 
t 

600 

.83 

Palomares  Irrigation  Company 

'1909     !^ 
i 

600 

. 

.83 

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127 


Deciduous  Orchards  and  Vineyards 
TABLE  XLVI 


Location  and  source  of 
supply 

Year 

Acreage 

'Depth 
applied 
feet 

r  Remarks 

Sierra  Foothills 

South  Yuba  Water  Co. 

1909 

6,900 

2.62 

Bear  River  Canal 

1909 

5,000 

2.62 

t 

i 

Sacramento  JValley 

! 

Palermo  Land  & 

1 

Water  Co. 

1912 

33 

.75 

'Prunes 

Palermo  Land  & 

i 

Water  Co. 

1912 

10.5 

1.64 

'Olives 

Palermo  Land  & 

t 

Water  Co. 

1912 

10 

.80 

'Olives  and 

i 

'Peaches 

t 

i 

Yolo  Water  &  Power  Co.'l913 

14.2 

2.29 

'Prunes 

i 

i 

Orland  Project       '1914 

14.2 

.25 

'Young  Almonds 

i 

i 

San  Joaquin  Valley 

i 

Turlock  Canal        '1909 

37.8 

.38 

'One  irrigation 

Pumping  plants  at 

t 

L.adera             '1910 

222 

.86 

'No  irrigation 

Fresno  Canal         '1910 

160 

.49 

*0ne  irrigation 

San  Joaquin  &  Kings   '1906 

t 

River  Canal        '--07 

104 

2.64 

t 

San  Joaquin  &  Kings   '1907 

t 

River  Canal        '  —  08 

15 

2.38 

t 

Pumping  plants  at 

i 

Friant            '1912 

20 

.83 

'Two  irrigations 

Pumping  plants  at 

i 

Friant             '1912 

150 

.06 

t 

i 

i 

Southern  California 

i 

Santa  Ana  Valley 

i 

Canal              '1912 

15 

4.83 

'Walnuts 

Santa  Ana  Valley 

i 

Canal              '1912 
t 

21 

3.18 

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